Has anyone tried the always an esper patch on version 1.1 ?

Heh, nice way to ask two questions at once!

And no I haven't, but it says in the patch readme that it applies to both v1.0 & v1.1, so it should work fine. Or were you wondering something else about patching it to a 1.1 ROM??

As for the potion thing, FF (the highest hex value for 1 byte) = 255, so that's why that's the max, it uses just 1 byte to allocate the HP. You would probably have to re-code it in such a way so that it instead reads from 2 bytes. Someone else can probably give you a better answer for this.