10 hours practice are not that much to feel fully confortable with the machine, so to me it doesn't look like the machine is winning the war, more like the war has just started.

I hope that you can find the motivation to go on soon-ish, so that you can gain more confidence and then start doing mistakes like the pros :) (i.e. because you're tired, on a deadline, trying to take shortcuts etc.)

IMHO the important bits to call something a success are:

* that the result is structurally valid (and this is a bit less important with a costume, which only has to be worn a few times)

* that the outside looks good

* that in the inside there is at least one error less than the previous project (unless this project was significantly harder than the previous one, in which case of course having more hidden errors is fine :) ).

(btw, for some of the issues, it can be helpful if you can get somebody with some experience to take a look at the machine as you're using it: thread breaking and the reverse not looking good looks like a tension problem: it may be because the tension you've selected isn't suited to the fabric. With the mechanical models I have experience with the solution is usually to play a bit with the upper thread tension while making tests on a bit of scrap, while the lower thread tension is usually left as is unless it has drifted significantly. I have no idea what to do with the electronic machines, however.)