No problem glad to try and help
The disc looks
like it has about that mileage (10K) judging by the meat left but can't say for sure without maybe a comparison. I've had 2 ACT pressure plates and both had a little bit of wear on the fingers where the TOB rides. Not sure how deep is too much but mine was probably .030" deep and been using it for a few thousand
is a good thread I updated on identifying ACT clutches via the diaphragm fingers, although I don't know exactly what number a 2900 would be. It might be MB-010XX or just a 3 digit number
Sorry, I don't know much about that collar situation. Mine looked about the same but never measured it
I'd like to be able to help more than that but I'm not going to guess on something like that. A wise man / more knowledgeable person should drop some insight!