1] Can the 1995 Land Cruiser be towed 4 wheels down without disconnecting the drive shafts? The answer is in the Owner's Guide (manual) for the SUV. Toyota doesn't allow me to see the on-line Owner's Guide for a 17-year old Land Cruiser, so I can't check it. I suspect the answer is it can be towed if it is a stick shifter, but not if it's an automatic. But only the Owner's Guide will know for sure. If it cannot be towed, 4 wheels down, then one answer is to rent a U-Haul car-hauler trailer to carry the Land Cruiser.
2] Can you tow the weight of the heavy SUV without exceeding the GCWR of the motor home? Probably not, but it's easy to check. Load both the motor home and the Land Cruiser with everything that will be in them when on the road. Go to a truckstop with a CAT scale and fill the motor home with gasoline. Weigh both rigs and add the weights together. Compare the combined weight with the GCWR of the motorhome. DO NOT
make the trip if you will be overloaded over the GCWR of the motor home. Even if you take I-10 all the way, there are some steep grades in west Texas and Arizona that will do you in if you are overloaded.
If you are right up against the GCWR of the motor home but not overloaded, then you have to worry about the automagic tranny in the motorhome. Personally I wouldn't try that trip without a tranny temp guage, then never allow more than 225° tranny temp. That 460 engine is going to drink a lot of gas, but you can plan for that. However, if you overheat the tranny and burn it up, that's going to be an expensive and time eating delay to get it back on the road.
One precaution I would take to help prevent tranny problems is to change the ATF to Mobil 1 ATF, using the procedures in the following link. Your motor home probably has an E40D tranny, so even though you don't have the exact engine/tranny combo those procedures were written for, you can easily adapt the procedures to your rig.
Changing ATF: 7.3L PowerStroke Engine and 4R100 Automatic Transmission. - Diesel Forum - TheDieselStop.com