Just edited to add, thanks for posting pics. It's hard for most of us to put our rough first attempts out there for comment. I always like it when I see someone's first attempts and then a couple of years later look at the same person's current work and see the progression from beginner to a high level of skill. You obviously have a clue, it's a matter of practice and getting the details right.

I'm no TIG welder, so take this with that in mind. You didn't get any penetration. Of course, your tubes are thick, so that makes penetration harder. I have no idea if an experienced welder would tell you to go back and practice on sheet metal, but that sort of thing never hurts.

I urge you not to take risks with your health, 4130 is not that expensive. Get some from McMaster-Carr. If you order now, there is some chance it will be there tomorrow, definitely Monday.