Part II,
I kind of doubt you are under 3k. Definitely under 5k but probably somewhere between 3k and 4k lbs.
1600 dry
400 motor
800 alum trailer
fuel @ 7 lb/ga
batteries, anchor/chain, gear, tackle, refreshments, tools, rigging, etc. It adds up pretty quickly.
Bushwacker recently sent me and some others a tally of towed weight on his Seafari (loaded for distance travel) and came in about 4600lbs including trailer. Granted you're probably don't typically carry as much gear but can carry 2x the fuel.
I'd definitely consider a true half ton or maybe a 1 generation Tundra as a base line. I know Bigshrimpin trailered his Seafari cross country with a little Jeep pickup but I think he said he was in 3rd gear a lot. I tow my Seafari with a V6 T100 w/5200lb rated tow pack. While it tows just fine, I don't feel it has the the mass, power, or limited slip to do the job safely... I don't even bother trying to move the 21 with it... I'm presently looking for a new tow rig, too. 2nd gen Tundras sure look appealing but kind of out of my $ range. Good luck.