Do be careful with trying to keep pushing your machine more & more. Timing issues are rare but potentially catastrophic to machines & continuing to try to operate it after attempting fix it yourself could cause even more problems (I'm not admitting to anything, but I may have had to learn that lesson the hard way myself -- ok, I'm guilty as charged. Back when I first started sewing on a regular basis, the timing on the Singer 353 I inherited was off & I just kept trying different things to "fix" it; by the time I finally took it in for repair, the rep told me I had caused an additional $60 worth of damage to my machine & that it would take 3 weeks instead of one to do the repairs because he had to special order parts. He's now serviced my machine for the past 15+ years & is super honest and affordable, so apparently I really did do a number on my poor little machine)
You've already done a thorough job of addressing all the possible options for needles breaking that one can resolve without the help of a service tech. A machine that's out of time can cause additional problems -- like a warped needle bar -- and it's just not worth it to keep trying to run the machine even briefly.
If you're on a deadline with your quilting project(s), you might look into whether any of your LQS'es will allow you to use/rent time on their classroom machines. I know a couple of stores by me give customers that option (one lets anyone use their Berninas free as long as they're sewing fabric purchased at their shop there isn't a class in session; another one rents out the use of her Sweet 16 by the hour; the third one sometimes lets customers come in & use the machines outside of class if they are servicing her machine and it's taking more than a few days). Hope you can get it fixed quickly! I always feel like I'm missing a part of me without my machine.