I tow a 7X10 enclosed trailer behind my 2004 2500HD with a Sunlite 850 TC. I have e-tracks set up along both sides of the floor and a few on the walls to hold other "stuff". I used TEK screws too, but without the pilot. I also have both ends and the middle bolted down with nuts under the trailer - probably a little overkill, but don't want the ATV bounching around inside. So far it stays real tight. I will be putting a new trailer hitch on the truck when spring finally reaches MInnesota - probably July!
As for the tie-down question - I have a single small strap for the front of my ATV and then two ratchet straps in the back. Each strap goes from the back bumper to the e-track on the same side. I take a little of the spring out of the suspension in the front and the back, and lock the brakes on the handgrip. So far - it has never come loose after about 30 times hauling.