The "second one is invincible" reminds me a bit of R-Type and the invincible option you get to accompany you in that series. Certainly an interesting, but quite tough idea!
I did get to the ETA 2154. I am not quite sure how things worked, though. Some enemies (especially the upper left one in the first room) seems to register hits only rarely, and it seems as if I could get the control boost by simply shooting an enemy while it was in front of a reflector.
I did resort to that to beat it - I wasn't able to line up the shots well enough. I think a little work should be put into the player shots and having them last a bit longer, so you can do proper trick shots :) Still, nice work!