If you have broke something what do you do

Obviously the mechanic is not getting down to the real
issue for some reason
Try a different shop
I can only guess but it sounds like you may need
a new ignition switch & then the proper adjustment
if one is required
You may be able to dajust yours to work ok if that
applies.
Seems odd the mechanic spends all that time in one area
& doesn't have a solution
You may have a bad door switch as well

pull the kicker case cover, probably something simple jammed up in there...if you didnt break her in keeping revs under 2000rpm for 10-20 hours you may have broke something internal again, lets hope not

the bobbin case may need to be replaced. it wouldn't hurt to have the machine serviced to make sure the hook & hook race are ok

Abby, I'd look to the place that replaced that expensive bearing assembly. That's the first thing I'd do. The other possibilities could be serious problems, especially if it's 4x4. We don't even want to go there. That possibility would be a shreaded front differential or axles.

Certain stitches you do, require different base plates...by the base plate, I mean the metal piece that the needle passes through when it goes down through your cloth and through the hole provided...This sounds like why it's breaking, I think your needle is hitting the plate under it. It may not be all that obvious, but it wouldn't take much to snap the needle. You may want to check your setting and make sure it's setup to do a regular stitch. If that's not it, then you need to make sure that the needle is in straight, though I believe putting on in crooked is hard to do.
I hope this helps.