Hi,
1. and 2. Turn off the "Use AJAX when possible for add to cart buttons" option of the configuration and that should help on these two issues.
3. I did the whole process on your test website at
teststore.solid-run.com/
and I didn't get any error. I remember that we indeed had such bug but it was already fixed and I can see that you have the latest build of the 2.2 version so maybe you did a new update in between. You should not have the problem with the latest build and as far as I can see, you don't.