More input needed: How do I fix this chair?

I got this lovely chair a couple months ago at a lawn sale. The people were moving and really just looking to get rid of their stuff, so they sold it to me for $5. I was very excited-- I love the shape, and the fabric isn't so bad either. I thought it would be a great chair to put in my bedroom, and Franklin has really enjoyed it.
It does have some problems though-- the upholstery is largely fine. There is a little discoloration on the seat, but I think that's just from age. The cushion, however, has real problems. It is lumpy on top, and you can see why when you turn it over. The brown fabric should be laying flat, and the white piece is the foam- that also should be flat, not bunched up on the right side there.


So my dilemma is this: I'm afraid then only way to fix the seat is to take the upholstery off the chair to fix the seat, repad, and put the reupholsterly back. However, I am concerned that I won't be able to reuse the same fabric. I like this fabric, but also the bottom is really messed up. I have scoped out some fabrics at Joanns, and here are some options:
(All swatches from Joanns.com)


So you get the idea. I'm looking for a blue and brown or teal and brown pattern to match the colors in my bedroom already. I'm a fan of