Looking at the last picture, the subframe looks bent but it is probablly an optical illusion. Is the whole frame bent or is it just a dent on the underside? Assuming it is just a "dent," you really didn't cause much damage. Uni-body construction vehicles gain strength by the ENTIRE CAR, not just a frame or a part. What you DID do is to create a weak spot. In a severe crash, it will probablly bent there first, but by then the whole car is gone anyway.

If the frame is BENT not just dented, you will have to have it looked at by a collision specialist, not just any garage.

I don't know where you live, but if you live in a snow belt and municipality uses salt (road salt), any penetration you have in the undercoat will cause rust to start there and it will spread quickly. You should fix any nick/gouge/break in the pant surface. Sand off any existing rust, put a primer on it, put a second coat of primer on it, then put a rubberized undercoat on it. As appearance is not a concern, you could probablly have it done VERY cheaply at a bodyshop if you don't want to do it yourself.

You probabbly know this by now, but be careful when you work on any car. Research, study, plan, and doublecheck everything you are about to do BEFORE you start. You could easily hurt the car or yourself, or worse, completely destroyed (or dead if you are underneath). What you did is an honest mistake but it does demonstrate lack of basic knowledge/safety precaution on your part. What I suggest is for you to check out some automotive textbook at a library and read-up before doing any more DIY repairs.

Stay safe!