FIXED AT LAST...
Yes folks, the outstanding service of Carver Equipment has come through once again. Thursday 4/21 a Carver service tech showed up with bags of hardware, locktite, and an impact gun. Every nut and bolt on the BH subframe was removed, reinstalled (or replaced as needed) with lock washers (and locktite red), and torqued. While there he also brought a filter for my 35 hr maint. and a note pad to address any other issues I noticed with the tractor.
Ten hours later and everything is still tight as it should be. I stop to check every few hours so I won't make things worse if they do loosen up, but so far everything is holding as I expected it would.
Thanks to the fine folks at Carver for followeing up and sticking by me after the sale (even 250+ miles away). It confirms that my decision to deal with them was the correct one.