I tend to remain sceptical of anyone making claims without valid and reliable data. With that said, some practices you list are of critical importance; others, I'm not sold on one bit. Please don't take this a slight against you, but rather as a criticism of your general claims (and lack of scientific data therein). Moreover, if you enacted all those changes at once, you'll never know which one made a real difference, and which one did absolutely nothing. Proper scientific methodology calls for the manipulation of one variable against a control (unless you want to run the more complex ANOVA).
Clean your MacBook Pro fans from within... it's simple, open the
bottom closure and blow the hell out of these fans
Absolutely. This is by far the most effective way to ensure your system continues to operate nominally over the years. It is sadly also the most neglected. Dust sticks to the blades (and most of the internals) creating a "sticky" residue and not only prevents the fan's blades from spinning at their optimum, but seriously restricts air flow. Computers generally accumulate far more dust than people expect. Regular cleanings are essential!
Download and install Fan Control and run your fans @ 2800-3000 RPM
This of courses comes at a sacrifice to noise (increasing it) and I'd like to see data on how much cooler the chips operate with such a small increase to RPM.
Ditch all browsers to Safari, I tried them all Firefox up to version 5
and 7 (Aurora), Chrome and Opera... nothing beats the CPU usage (less
of it) than Safari. Also flash youtube videos run with less resources
on Safari for some reason
Again, I'd like to see some data being this claim. These guys have conducted some very loose tests that support your assertion, and I'm inclined to agree that Safari, being so tightly integrated into OS X should net improvements over its competitors across the board, but a few CPU cycles here and there aren't going to amount to a drop (drastic or modest) in temperatures (these saw extremely small differences in performance).
Use your faster GPU on AC Power, and lower on Battery power (use
http://codykrieger.com/gfxCardStatus for source-based GPU switching)
GPUs put off heat, wether they're integrated or discrete. I can see a reduction in power, but a reduction in heat, again, I'm not sold. In the case of MBP, models that possess discrete video cards have dual fans (one for the CPU and one for the GPU). So using the discrete card may kick off additional heat, but it's also got a dedicated fan to push that heat away from the machine. Stressing the integrated chip will see the CPU spike in temperatures, which means that fan will be doing more work to handle the additional load. It may be the case that the fan on the CPU (together with the integrated GPU) may be sufficient in pulling away the excess heat, but at no doubt the cost of excessive noise (generated by 6,000 RPMs). I don't know if anyone has done testing, but from my own anecdotal experience with my old MBP1,1, the GPU fans rarely switched gears (unless playing intensive games and then the issue would be moot as you'd want to use the discrete video). It was always the CPUs fans that took the brunt of the work.
Replace your internal hard drive with an SSD
Not only will this greatly improve performance, but it can't hurt in reducing temperatures. The idle/active power consumption of an SSD is about 0.5W to 2w, respectively. The average power consumption of a traditional HDD is about double that (1W to 2.5W, respectively). I won't know what that transfers to in the temperatures department, but it certainly can't hurt.
Keep your monitor running @ 90% brightness and keep your keyboard lights off or low
I'd love to see data on this. LED backlighting is already quite efficient and distributing heat, but I'm not sure a reduction (at least that small) in power would have any effect. As for the keyboard lights, those are LEDs and as is with such small LED bulbs, they are incredibly power efficient and produce little to no heat as a result.
With all that said, I'd saying re-application of Arctic Silver 5 (or thermal compound of equal quality) and the cleaning of dust from the internals is the most effective (and proven) way to keep your system cool. I've never seen data to convince me that turning off some service, or placing your system on a pad with a couple of fans does anything (other than perhaps keep the case cooler to the touch) worth merit.
Best Answer
SMC Reset
To your minor question: I do not think the absence of the battery should affect the SMC reset. Source: I have successfully done this with an older mac with no battery and corrected fan problems.
Key Observations
Since it is not obvious what your problem is, I will cover some bases starting with some key observations:
You did not mention resetting the NVRAM/PRAM which I also did when fixing my fan issue. Have you also reset the PRAM/NVRAM? That would one of the two immediate troubleshooting steps I would do with something that looks like a firmware issue. (I believe you hold down the key for 3 chimes btw… not sure if it tells you that on the site.)
Since your diagnostics do not appear to be reading your CPU temperature accurately (it should definitely not be 0C (34 degrees F). I would try again with a different diagnostic, and/or repair permissions using diskutil, run with sudo to ensure the program is able to access the requisite files to generate real output.
Troubleshooting
Some possibilities and thoughts to facilitate further troubleshooting:
While in diskutil I would check that your drive is in good health. HDD's only operate for 5-10 years. My 08 pro has a dead drive… it may be working hard to keep it at a low temp so it doesn't lock up? Physical wear on the drive can also generate heat.
I would check out your system diagnostics to see if anything is hogging resources. Assuming your hardware isn't screwed up and it's not firmware, I would check to make sure the kernel isn't panicked or some weird unrecognized process isn't interfering with your system.
I note that without an intermediary battery your computer may not be getting a completely regular power source… what comes out of your wall may be lower or higher voltage than expected. Sometimes that generates heat and causes fans to go insane. Sometimes that can "zap" files. You may wish to reinstall your OS without deleting your files and configurations, to make sure everything is in good order.
You may also wish to get your hands on a battery to see if that makes a difference. These cannot be too expensive nowadays… someone may have one laying around. The fact that yours once exploded also… you may be able to get one from Apple even if you're not covered. They really don't get a lot out of keeping and warehousing old parts (why applecare is a good money maker for them) and like happy campers and I think that battery was recalled no? You may have been entitled to a new one years ago anyway.
You may also have already tried this but checking the logs at /var/log/system.logs (hard to parse) may provide a big picture view of what's going on with the fans even if it's not entirely understandable or easy to get through… sometimes the error messages are verbose and incredibly precise. Hit or miss. It will be FULL of entries that don't matter, but may tell you quite clearly what's going on if you just do a find for like "fan" "heat" "power" "voltage."
Finally (albeit obviously) you may want to make sure you don't have a ton of crud clogging up your fans or blocking. Cleaning a computer directly or with air can easily mess things up… but yeah… this may be necessary. If a sensor cannot get a read on heat or a fan is covered in gunk it may run the fans at full just to get normal cooling in order (first case) or because it's designed to be cautious about the heat issue (second case).