sorry I cannot help with the cam gear issue.
I just wanted to add a little on the clutch shudder.
Clutch lining is like brake lining, in that, ANY amount of contamination on either surface is going to cause an issue.
I'm not talking about the obvious oil leak , but more the original installation technique.
Don't even put your fingers on the lining.
We all have different levels of body oil and acid in the pores of our skin , if you know what yours is like , then fine. Otherwise play it safe , don't touch the linings.
ps, rear main oil seal leak doesn't normally affect the clutch, it can look bad running down the flywheel , but with the engine running , the oil is thrown off onto the bellhousing.
It does sound like the rear main seal was installed incorrectly , but there may well be another issue to explain the clutch problem.
eg, dirty/greasy fingers on the lining , or pilot bearing grease flung onto the lining , or excessive spline lube also flung out onto the lining .
Clutch shudder is also affected by soft engine mounts or bad flywheel/pressure plate run out.
