Serious problems with the early EcoBoost F-150's? Extremely misleading and patently untrue. The had some issues with a minute amount of trucks stalling under very certain conditions, and they have a FREE fix for it. Most trucks will never see that problem. Also a minor amount of coil packs going bad, its a $85 part and anybody with a couple of tools can change one in a half hour or less. That does not add up to "serious problems". The 3.5 EcoBoost has been out longer than the 5.0 that you're cheerleading (3.5L Eco first available in March 2009 in the Flex). The current 5.0 is a good engine, but previous editions of the 5.0 are completely different engines.
Please don't attempt to spread unfounded or untrue statements.
As far as an Eco towing the OP's TT, no problem. A 3/4 ton would be better, only because its heavier. The trade-off is you're going to get almost half the fuel mileage when not towing. My experience towing with the Eco is over 11 mpg. Normal driving 18+, highway much more, deduct 1.5 mpg in the winter unless you use 91+ octane fuel.
And as far as the torque available only in higher RPM's, also totally untrue. 90% of the EcoBoost's 420 ft lbs of torque is available at just 1900 RPM.
An EcoDiesel (cute name, wonder where they borrowed that one from...) has very little payload. And its a $4000 option. You'd likely never make that back on fuel savings. You're much better off getting a hemi if you go Fiat/RAM.