Use the envelopes with dots next to them, in the amp envelope page, that way they’ll always start from the beginning of your attack phase no matter where they are up to at the next note-on point. However, it can still sound a little unsatisfactory depending on where the last note is decay/sustain/release wise, such are the limitations of working with monophonic tracks.

Advice on the pad sound you’re trying to create could only be given with detailed knowledge of exactly what it is you’re after and that stuff is just as hard to put into words as it is for others to accurately interpret.

EDIT
Wow I type slowly.