Almost all of the keyboard shortcuts you've learned on Windows are the same on the Mac. The difference is which modifier key you use to invoke them.
On Windows, shortcuts are typically invoked with the Ctrl modifier key.
On the Mac, you use the 
key, also known as the "command" key. It's in the same physical position as the Alt key on a Windows keyboard, but is nothing like the Alt key.
The Mac has its own Alt key, labeled Opt/Alt. Its primary use is a secondary modifier for keystrokes. Command-Option-S might be "Save As", for example, while Command-S is regular "Save".
The Ctrl key is there on a Mac keyboard, too, but it's hardly ever used for anything.
The relative layouts look something like this:
PC: Ctrl Windows Alt
Mac: Ctrl Opt/Alt
The problem is that you're most likely using a PC keyboard on your Mac. In that specific case, the Opt/Alt and keys are reversed. You can change this in System Preferences, under Keyboard. Truly a huge pain in the rear for switchers. That layout looks like this, instead:
PC keyboard on Mac: Ctrl Opt/Alt
Apple's website has some pretty good hints and tips for Windows switchers. Start here for answers to your specific question about keyboard shortcuts. Then go here and read everything!
At first I thought that maybe you had a firmware password enabled, but some of the stuff you mentioned doesn't line up (being able to reset the PRAM, and choose a startup disk at least some of the time).
Have you checked to make sure that you've got all the updates? Specifically, the keyboard firmware updates?
Best Answer
Use altwindowsenter to indicate you've finished a piece of text and want to move on to the next section, possibly creating a new slide.
Use esc to escape from whatever you're editing, then use tab to move from text to text within a slide, and use Page Up and Page Down to move from slide to slide, and use Enter to start editing a text.