Welcome to the Hi-Lo family! You have a rare jewel in that 31-footer. Only a few were made, as far as I've read here on the forum.
On your towing question, I hate to tell you this, but unless I'm badly mistaken, your Ford Explorer is seriously under-powered to tow that much weight, and you will be in an unsafe condition driving that rig.
Towing can be quite confusing, so here's a website that has a lot of info:
Can you confirm the 8500 lb number you mention? From looking online at the specs for your 2007 Explorer (without knowing which engine and trim package you have), it looks like 8500 lbs is the Gross Combined Weight Rating (GCWR), defined as, "a specific weight determined by the manufacturer to be the maximum weight of a loaded tow vehicle and its attached loaded trailer. The total weight of the tow vehicle and trailer should never exceed the manufacturer's listed GCWR". If your GCWR is 8500 lbs, that's what Ford says that the Explorer is capable of pulling down the road....pulling itself and the RV, loaded with fuel, passengers, food, pots & pans, clothing, toiletries, etc.
It looks like your Explorer weighs somewhere just over 4000 lbs, which means, when you factor in the rule-of-thumb 10%-20% safety margin, your Explorer (again, if that 8500 lbs is indeed the GCWR), can safely tow an RV about half the weight, or less (depending on weight of cargo and passengers), of your Hi-Lo. Sorry, but that's how it's looking. I have a 28' Hi-Lo and tow it with an F-250 diesel, although I'm sure a large gas-engine in that frame would also pull it safely.
The 3500 lb number you mention is likely the weight limit of the hitch (the metal bracket and ball assembly that is bolted to your Explorer's frame). The 3500 lbs figure tells you that the hitch itself is engineered and constructed to tow up to 3500 lbs. Because the hitch was engineered with a sizable safety margin, you are able to tow the Hi-Lo with it, but don't count on doing that forever.
Not sure where you are in Texas, but the Escapees organization is headquartered in Livingston. They conduct a couple of "RV Boot Camp" schools every year, on weekends. You might find that a useful experience. They will also do a full weight analysis of your rig and do an evaluation and make recommendations. I think they'll do that weekly at their RV park in Livingston.
You can find info on that school at this link: https://www.escapees.com/education/rvers-boot-camp/
Others will chime in shortly, and correct me if I'm wrong. Let's hope so!
Otherwise, once you get an adequate tow vehicle, you will be ready for great fun in your Hi-Lo!