looking so beautiful!
I don't use feeding charts or weights, I go by feeding something no larger than the thickest part of the snake's girth.
A small bulge is fine, you don't want a big bulge though (pythons are better at handling oversized items, not to say a boa can't... just in general)
A f/t adult mouse or f/t rat pup should be fine (I usually try to switch my boas to rats pretty quickly if they don't take them off the bat)