I would keep it under 65 mph.
Big problem is the dry hitch weight of 385 lbs on that TT. 385 does not include battery, LP tanks, or any options. So add your battery and two full LP tanks; 2/3 of that weight falls on the receiver. Now add 90 lbs on the hitch receiver for your WD hitch, too. You will be over 500 lbs, I can almost guarantee it. And that is before you add any water or gear.... and is the fresh water tank under that front bed?
Been there, done that, bent a rear spring, and lucky my hitch receiver didn't tear off or anything catastrophic... I had a 23' Rockwood with dry hitch 380 and a 2000 Merc Mountaineer with 6000/600 tow rating.