How much to shave off the cylinder head.

I took 0.070 off the head and another 30 off the block, wish I'd have done more. Especially since damneer any head gasket you're gonna find will be at least double the thickness of the original. So the first 20 or so you have milled will only get you back to where it was from the factory.
Those prices you showed for the mill job seem a little crazy, but I dunno the machine shop you 4 using or what part of the country you are in.
Even if it took a little bit longer to complete the job id definitely do the cam while it's apart this time. Alot easier to do while it's apart for the first (and hopefully only) time.
It will cost more to put a cam in later as well. More time wrenching, more more gaskets, more everything.
What cam did you have in mind? New? Reground? I see people that have cams for sale here and on the /6 site now and then, you might be able to save some money.