I'm still trying to figure out what's going on with all three of these
issues, but i'm not making any progress.  I have determined that, for
issue #2, the problem can be masked by manually loading the nfs module,
preventing it from being auto-{,un}loaded as a dependency of nfsserver,
which in turn is a recently-introduced dependency of compat_netbsd32.
(This is similar to the work-around for issue #1 where manually loading
the mqueue module hides the issue.)  Without this dependency, the
compat_netbsd32 module fails to load because symbol do_nfssvc is not
resolved.
If anyone has any ideas on how to make some progress, I'd be happy to
try them out.  At least I can recreate two of the issues in a qemu
environment without putting my production box at risk!
Hooray!  Issue #2 (below) is resolved with the following commit
	Module Name:    src
	Committed By:   pgoyette
	Date:           Mon Nov  2 09:57:43 UTC 2015
	Modified Files:
	        src/sys/nfs: nfs_vfsops.c
	Log Message:
	Don't forget to call nfs_fini() when we're finished.  Without this,
	we leave a dangling pool nfsrvdescpl around.
	To generate a diff of this commit:
	cvs rdiff -u -r1.230 -r1.231 src/sys/nfs/nfs_vfsops.c
One down, two remaining.