I'm going to say the following in the belief your front end (suspension and steering) is tight and there haven't been changes or damage there...
Thanks to efforts to standardize in the tire industry, you can use one manufacturer's Load/Pressure Chart for other manufacturers' tires.
Michelin's chart is easy to find. Go to your "LT225/75R16 E" tire size and you'll see that 65-psi in Single (front axle) service carries 4670-pounds. The Door Jamb Sticker from Ford shows GAWR-F (Gross Axle Weight Rating - Front) as 4600-pounds.
Up through 2007, GAWR-F for E450 was 4600. Typically the coach builder only repeats Ford's numbers.
What we need to do is use the rest of a chart like Michelin's. Load your coach like you would for an RVing trip. People, supplies, tanks, equipment. Take a jaunt to a truck stop with a CAT scale. Tow your toad if you have one. For $10 you get legal-for-trade weights for Steer/Front, Drive/Rear, and Trailer/Toad.
I'm going out on a limb and guessing you do not have close to 4600 on that front axle. Most Class C's have a long rear overhang with a relatively short wheelbase. If you have 4000-pounds on the front axle, you need to come down to 55-psi. 3800? Then only 50-psi.
Make adjustments and take another test drive. I don't want you getting new tires, overinflating them (relative to actual load) and being in the same position you are now. Fords are very sensitive to front tire pressure when it comes to tracking on the road. The rear axle weight will be informative. Hopefully below GAWR-R and you can reduce pressure a little for better ride, but rear won't affect tracking.
At least the tire installers didn't "sidewall" you. You know, "Says 80, put 80 in all six." That just happened to us on a set of new tires. Went over a high bridge with some crosswind. OK going up. Downgrade unloads suspension a little and the RV became nearly uncontrollable. Stopped as soon as I could and tire gauge showed 80-plus. Dropped pressures to 65-plus and the rest of the drive was OK.
Know and verify the right pressures for your coach, your load.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB