I have a 2008 Mazda Tribute with factory tow package, which I'm sure that you know is a rebadged Ford Escape. Mine has the 3 litre engine producing 200 HP, which is 40 HP less than yours. I also have a four speed transmission with overdrive-lockout vs your six-speed tranny.
To accommodate trailering, I've replaced the transmission fluid with full synthetic as advised in the owner's manual (about a $120 cost for fluid plus 30 minutes labour for a flush). I've also added an aftermarket transmission cooler (very reasonably priced at $80 for parts plus an hour's labour), which makes quite a difference during long, hot hauls.
The RP-177 has a beefier 4" frame to accommodate the slideout, compared to the RP-171's 3" frame. So, yes, it is capable of handling more weight. I'm not sure what type of cargo you're talking about carrying in your trailer. We've got just under 300 pounds of gear that we carry, in addition to the A/C, microwave, battery and propane that aren't included in the trailer's dry weight.
Speaking about calculating weights, don't forget about fresh water & waste water. We usually run with 10-20 US gallons of fresh water in the tank. Although many people drain their fresh tank before heading on the road, we find carrying a bit of water very convenient for washing dishes after a picnic stop while travelling, simply using the loo, or showering after stopping at a beach. And there are times when its necessary to travel with 10-15 US gallons of black water because a campground didn't have a dumpstation (e.g. dispersed camping/boondocking), or because we stayed didn't stay at a campground at all (e.g. WalMart, family's/friends' driveways, open field during a concert/event). I like to have at least 300 pounds of leeway for water & waste on these occasions.
Tongue weight was a major concern when I purchased our 2009 RP-171. The dry tongue weight on an RP-171 is 181 pounds - fully loaded ours comes in at 225 pounds. The RP-177's dry tongue weight is 232 pounds. By the time you load up the trailer and add a battery and propane, it'll be topping 260 pounds. I know that the Tribute/Escape lists the tongue weight at 350 pounds, but you also have to give some consideration to weight you're carrying in the back of the vehicle. IMHO, you will likely need weight distribution if you choose an RP-177; this means you'll also need to install a class III hitch in order to support the WDH. I do have a friction sway bar installed on my trailer and class II drawbar.
But, the proof is in the pudding as granny used to say. We travel at 55 MPH, but are able to speed up to 65-70 for passing. Anything above 55 MPH is clearly working the engine/transmission and makes me feel uncomfortable. Gas mileage is in the 10-12 MPG range, which seems to be typical with other r-pod owners and their various vehicles.
However, with all that positive stuff I've said above, I've always maintained that I don't recommend towing an r-pod with a Tribute/Escape. Its just too underpowered. The vehicle's performance is just barely acceptable while towing an r-pod at 55 MPH. A vehicle with a 5000 pound tow rating would be much more appropriate for an r-pod.