Thanks so much for releasing the latest source code, for someone still learning the ways of the 6502 this type of stuff is invaluable. Looking forward to comparing the two versions of the source code!
As far as the speed of the latest version goes, comparing it side by side to the Spectrum version I think your version seems to be slightly faster than the original Spectrum version so your goal has been achieved.
Good idea to be able to select frame skipping on/off in the final game as I'm sure there will be a difference of opinion over which method is best.
I've not completed the game yet (it's quite a hard game even with endless lives!). I have activated some of the pyramid things and not found any problems yet. I will report back if I find any problems or if I'm able to complete it.
Thanks again for all your work.