I'd check out a couple of jackets at your LBS to get an idea of how they are done. I don't do a lot of clothing but I'd serge the edges for a neat clean look. Otherwise you have to fold over the seams and topstitch to make it look clean and keep your fabric from fraying. I don't know how much sewing you do.

Keep your jacket as simple as possible. Since you said your fabric is already lined with fleece you shouldn't need to add extra lining. I'd draft your pattern on muslin to get the fit right and then sew up the jacket.

I don't know what you would use for gripper elastic. When I checked out the jackets it said it was draw cord hemming.

You may need a teflon foot that is made for easier sewing if a regular foot/walking foot isn't working right.

Would it just be easier to buy a cheaper jacket for now?

Good luck!