Well, I can try to help. Who knows if I'll really be able to answer your questions like you want. I'm not a fan of t-shirt type fabric, since it can do funny things.
#1: Your first recon didn't turn out all that bad, to be honest. I'm sure it feels that way to you cause you know all the little spots, but in the pics, it's not as horrible as you think.
#2: As for it getting bigger, I'm not really sure. It might've had a lot of seam allowance, and when you took out the seams or whatever, the extra inch or so made it bigger. Or, you could've stretched the fabric somehow.
#3: Yeah, even though it's a recon, you should always measure before you cut and make sure things are right. Unless you want that uneven, thrown-together look. But always, always measure first. Oh, and pin your fabric before sewing. That'll help keep it straight, especially stretchy fabrics.
#4: I don't think the top part was sewn wrong, I just don't think you took the time to make sure it was straight, etc. It not being lined up with the rest of the tee would make it bunch up like that at the armpit.
#5: It's okay if you never wear it, it was good practice and you probably learned a lot!! That's how we get experience and learn from our mistakes.
Secondly, I kinda think off-the-shoulder tees are a bit uncomfortable to begin with, but that's me.
#6: The underarms being too low is due to not measuring yourself first compared to the shirt you were using, to see how much room you needed. Or, you could compare with another shirt that fits really well. I could be wrong about this, but I think that's what it is. And it bunches, like I said, because it probably wasn't sewn on straight.
So, basically, you didn't do too bad a job! I hope I helped a little.