Surprising the nylocs loosened - maybe nylocs AND locktite with a little bubble gum ;-)
Btw, for leverage when tightening, I use a long screwdriver under the coupling and over one of the bolts on the opposite side of the one I'm tightening. Have also used a chain wrench. Left the transmission in gear just to stabilize it a bit, but took most of the force with the screwdriver.
Don't recall the exact bolt size, but you can google the torque - M8 Class 10.9 for example is 40 Nm.
Cheers, Craig, SN68 Sangaris, Tropic Isle Harbor