So what would you do, or should I say "what would be the thing for me to do being a novice"
I think your simplest least-risky fix is to trim the bolts.
Spin a nut on all the way. Use your dremel or even a hacksaw to get the length down to what you want. Do a little grinding to dress up the end, clean off any burrs. Unthread the nut (to clean anything else out of the threads)
One thing to watch for: If you're trimming bolts, you need to make sure you will have enough threads left to go into the hole, without the body (the unthreaded part) hitting. I wouldn't expect that to be a problem here, because you're not talking a lot of thread depth, and you've got bolts which are only a little too long. But keep an eye on it. If you end up starting with a too-long bolt, and you trim off so much of the thread that the body will hit the jug before it's down, then throw the bolt away and start with a shorter one.
After you've got your bolts trimmed, you're back to test-fitting to make sure you can snug everything by hand before torquing.
If this were my project, I'd probably tap out the holes. Some of my 7.6 machines are like that, presumably because somebody went through what you're going through; bought some bolts which were a little long. I'm advising not to do that in this case because it sounds like you're not used to using taps (the little stick looking part) and dies (the round part) to cut threads. The consequence of messing up a bolt is a new bolt. The consequence of messing up the holes in the jug is a new jug, or at least a repair with a helicoil or something like that.
You're almost there. Get those bolts sorted out, do your test fitting, torque that head on there, button her up, and go!