I had a few studs break one time on one of my 5200# Al-Ko axle drums.
I was removing the wheel to rotate the tires. But after getting new ones swagged in, there has been no further problems. Certainly nothing like what you've been having.
Are your new studs breaking or just the originals?
If the new ones are also breaking perhaps the 120# torque?
I only go 90-100#.
And have you weighed your trailer? Could you be exceeding 5200# per axle, 2600# per wheel? Normally I would expect your tires to go first if over-weight, but ...