Just installed openSUSE 11.3, and after 5 seconds , the keyboard goes to sleep for 1-2 characters

This unfortunately is a known problem in Opera spanning to OpenSuse 42.3. YouTube reports that H.264 and MSE & H.264 both are unsupported when accessed from that OS. This is using Opera 46.0.2597.26, not quite as fresh as yours, but newer OS.

Looking around the web, there is reference to a Chromium codec patch. Uninstalling Chromium makes no difference on my setup, nor force reinstalling ffmpeg after uninstall of Chromium's extra codecs. For those not feint of heart, there is a manual-linking solution [1] involving libffmpeg.so, which seems to have success there (but must be redone each time Opera is updated). I have not tried the manual linking.

[1] https://solus-project.com/forums/viewtopic.php?t=1004

From what I have read, you are out of luck using standard xkb because, as you have found, with xkb the output of a dead key combo is either zero (if the second key did not match a valid sequence) or one Unicode code point.

I do not have an Ubuntu running X to test on, so I cannot test this suggestion, but I believe the solution for you is to switch to using uim, which supports multi-codepoint outputs from dead key combos. You can read about how to set up uim at wikibooks or from this post (but do not follow the whole post, as it is solving a different problem).

The post I referenced shows how to get 'b to output the 2 character sequence 'b while while still allowing 'a to output the single character á. They solved it by making ' a dead key and then configuring the sequence dead 'b explicitly, and then repeating that for the 99 other characters on the keyboard. You do not have to go so far.

You already created the .XCompose file you need. Switching to uim should be all that is left to do.