Good news. I made new gaskets and the breather is now leak free
i ordered 1/32" Palmetto 2970 gasket material from McMaster Carr. It's fiber bonded nitrile with good temp and pressure specs as well as being oil resistant
[URL unfurl="true"]https://palmettopackings.com/2970.pdf[/URL]
It's actually actually .03" thick vs CNW's .022". This should make it a little more sturdy but it also means there's that much less bolt engagement. And it's also a bitch to cut. I cut it as close is i could to the valve to allow as much material as possible between the bolt hole and the valve opening. Even so, there's not much clearance. For added measure, i sealed it with Loctite 518. I put it back on and so far, no leaks 
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Oh, and i didn't need to go to all the trouble of loosening the gearbox and pulling the clutch. Idiot me, i thought i needed to remove the bolts when in fact all i needed to do was just get them clear of the mounting flange and then the housing, with the bolts, can be dropped. Oh well, live and learn
