You don't say what size or gauge the studs are, but regardless, any reasonable stud is more than adequate for the weights involved. I'm not fully clear on what your connections really are, but in general they sound adequate. Are you sure the bulge occurred during the installation and wasn't always there? Drywall walls are rarely perfectly flat when checked with a straight edge. If the bulge were caused by the installation, it is probably the screws pulling the adjacent stud out of plumb due to some misalignment with the other studs and/or the mounted devices.
Metal studs are rather elastic, it doesn't take much side load for them to deflect a few mm. Despite my uncertainty of what you actually did, I'm fairly sure you have no structural issues and do not need to worry about anything failing.
Do not use drywall anchors to hang a TV that large on a swivel mount. If it was a mount that didn't have motion, I might say that's acceptable, but not with a swivel mount.
You will need to use wood in some form to add the necessary strength.
Plywood can be attached to the wall studs using 3-1/2" lag bolts with fender washers. To provide a clean finish, the drywall can be cutout and the opening filled with the plywood. Then tape and mud the joints. Sand the surface smooth, prime, and paint. The plywood will be barely noticeable if done right. Be sure to match the plywood thickness to the drywall thickness.
If you do not want to remove any drywall, the plywood can be mounted directly over the drywall. You will need to use at least a 4" lag bolt in this case to account for the extra depth of the drywall. The plywood can be finished with a routed edge, sanded, primed, and painted for a finished look, if desired.
A final option for a truly hidden mount would be to open the wall by removing the drywall. Then install 2"x4" crossbracing between the studs at the correct locations for your TV mount. Replace the drywall, tape and mud the joints, sand, prime, and paint. The bracing is now hidden in the wall and you can attach the mount to the bracing.
Best Answer
Your TV is being supported by two pieces of paper. That should be all you need to know.
The white plaster material in the middle of drywall resists compression. The interaction between the shaft of the bolts and the inner plaster is keeping the load from shearing straight down the wall and will support a significant load.
However, on the front and back of the drywall are two sheets of paper that resists tension, similar to the purpose of rebar in concrete. And the interaction between the threads of the bolts and these two sheets of paper are all that are preventing your TV from being pulled out of the wall. Over time, the top bolts will pull out from vibration, temperature and humidity changes, and especially if you adjust the angle of the TV.
Once those top bolts start to pull through, the paper will tear, the plaster will shear out of the hole, and the TV will only be supported by the lower bolts under a highly leveraged load. Those lower bolts will immediately fail, and you'll have a broken TV on the floor at best, or a broken person that was hit by the TV at worst.
So, as everyone else has already said, remount the TV to proper structure.