2 different films makes no sense to me. Can anyone explain why one might want to do this? XPEL Ultimate can both be done via patterns without seam (which they have for M5) and with overwrap. On my 3, which isn't that much narrower, my whole bumper is a single piece with over overwrap.
You have every right to be pissed given what you paid. I had basically the same area done on my car with XPEL ultimate, and it was a grand -- i understand its not as cool or as big a car, but I think at the price you paid you should have gotten much better quality.
I would tell my installer to replace the whole bumper with XPEL ultimate, for free. I am sure there are plenty of forums, etc that your installer would not want that pic, your story ( to include what he charged you), and his name linked together.