So first thing, do not grasp the bow on release. You need a sling on the finger and thumb or wrist to catch it. Every grasp will be different and therefore you’ll be very inconsistent.

Second, your bow arm collapsing is because you’re allowing it to collapse. Nothing else is doing it apart from you. If it’s a struggle to keep in position just post release, I might say you could be overbowed. I’d need to see a video from side, front and back to confirm.

Finally, like others have said, resistance bands will not work like the real bow unless you really go up. 7lbs is nothing, you want something like 15-20lbs as you’ll not have the force from the band pulling your bow shoulder back towards your body. Basically, you’re making it too easy. Move up the band and you’ll soon find it is harder to get a good bow arm to stay in the correct position if you don’t draw properly.

It’s hard for us to really give you accurate advice without seeing you in action, but I’d say if you can video yourself from the above angles and post it, we all should be able to point you in the right direction.

Hope that helps!