I have sugestion, about pressing Y button for alchemy, do the script to skill numbers, where you put skills, and pressing numbers, there you put alchemy activation, and after closing NPC, cursor will move to that place. And about number of buying item:
1. You should make a script to pres 5x times on this place

2. You should remove 5x time moving from inventory to Alchemy window, and leave only 1x time, like, you buy 1 Armor or whatever, and alchemy only one, and then again.
I think 1st is better, but it's only suggestion, Do as you like.