Towing with Via/Reyo

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We just returned from a 1500 mile trip towing my 3,700 lb Jeep TJ with our 2011 Via (Sprinter chassis). I know a lot of people tow Jeeps with these, and others tow lighter 2300 or less lb cars like Chevy Sparks, Fiat 500s, Nissan Versas and Smart cars.
On the flats we had no problems but climbing some of the long grades we were down to 30-40 and on some 7-8% grades when a passing lane was available I slowed to 20-25 to let the oil cool down. Coolant never went above 228F and came down quickly, transmission never went over 205F and usually stayed around 183F (I added a transmission cooler before the trip) but the engine oil went to 260F and a couple of times to 267F. The Sprinter runs high oil temps anyway and most people don't know it because they don't monitor it, and only the newer VS30 Sprinter has a dash gauge showing oil temps and it is not a true gauge anyway. We never once ran the dash air instead running the coach air and generator.
Coming down the steep grades with my NSA Ready Brute with the Ready Brake I was not too pleased. I don't think the Ready Brake is ideal for a motorhome that has marginal braking at best (no engine/exhaust brake available for Sprinter) towing a vehicle that weighs a third of what the motorhome weighs in the mountainous West, which is where 100% of our travels are. Coming into the Salt River Canyon the front pads got hot enough to set the alarms on the TPMS and I'm sure they were smoking, and we could smell them. I was going as slow as I dared and near the bottom I had to brake down to under 10 MPH for a flatbed moving a D-9 with a line of cars behind it. To make the surge brake activate it requires quite a hard braking action even though I had the sling cable as tight as I dared with barely 2" of slack.
Need to make some decisions now, first of all I will probably consider a different braking system. I can still use the Ready Brute tow bar without the Ready Brake by just replacing the brake part with a $89 part.
Secondly I may consider a toad in the 2300 lb range, or perhaps go back to no toad at all and just rent one at the destination.
I really love the Jeep and I spent a lot of money on it, it has less than 12,000 miles on a new engine, transmission, clutch and cooling system and it looks like new inside and out although it is a 2000. But if it's going to kill my motorhome I'll have to either accept the fact that the motorhome might be short lived or give up the heavy toad.
I think most of the Sprinter based motorhomes that are towing a heavy Jeep have low enough miles that no problems have popped up yet, and most people don't realize the stress it is putting on the little 3 liter diesel which is severely choked by all the emissions it has.

I would love to hear from other Sprinter based RV owners who tow in the Western mountains and deserts.