My 2 cents, and to answer your question, the v6 will not be an upgrade over your ridgeline. The 2008 ridgeline makes less power but is faster 0 to 60 than the v6 ram is. Perhaps the 8 speed will help, but as others mentioned you're going to still see high RPMs, the Ram is much heavier and bigger. The rest of your experience will be better, more stable, probably more payload, but you're already thinking about a bigger trailer.
The hemi is the upgrade you're looking for. The v8 3.21 will happily pull your trailer and the next one as well, while still giving you equivalent gas mileage on the freeway if you drive conservatively. I regularly get 23 to 25 MPG sitting at an average of 63 mph and refusing to pass people etc.
Don't fixate on the rear gear ratio for what you're pulling. The high rpms is the problem according to you, and you won't get away from that regardless of gear ratio. It's not a magic bullet, it essentially moves your shift points down but your engine makes power by revving, your transmission and gear ratio work together to get you at 4000 rpms. You need to be there, doesn't matter what combination of transmission or rear end gears got you there, you need those rpms. The only place it helps you is from a dead stop, which funny enough, is the last place I'm looking for more power towing my trailer.
Otherwise (hate to say it), but look at the 1500's from GM, and the 4 cylinder 2.7 turbo. It has tons of low end torque, and gets decent MPG as well.