That looks really good! But are those bottle cage boss holes on the
back of the ST in the second picture? They can be filled in but I hope the BB shell is the right way round with the left-tighty side on the right. If it's not you'll actually be fine, just throw a bit of loctite on there. Have so far avoided that particular mistake myself but a friend got it on the wrong way around on a bamboo frame and I fortunately remembered his pain
Angle iron is not the best reference surface but it's good enough especially for a first frame. It's not like one's going to be riding the bike on a road made out of Blanchard-ground steel plates.