Your Equalizer hitch's weight is what, 100 lbs? That weight should be added on to the tongue weight of the TT. So now you're at about 568 lbs before you even put anything in the TT. And I bet your fresh water tank is in front... forget about carrying water while you travel?
Been there, done that. Had a 600 lb hitch weight rating on my Mercury. Towed a Rockwood 2304s, dry wt about 3400 and dry tongue 380 IIRC. Used an Equal-i-zer brand hitch. Guess what, I bent a rear spring on the Merc and needed new ball joints & tie rod ends soon thereafter.
All I can say is "good luck".
