handling improvements for a W24 chassis

Not sure, but 105 seems high.
A trip to a good alignment shop can make a world of difference. However, any RV takes a little getting used to. Yours however seems a bit extreme.

How many miles on the coach? Underneath you will see a round gray or white rubber "spring" that sits on top of your front and rear axles. This is to cushion the frame from the axle in the event of a large bump. The frame should normally be riding above this rubber spring. If the springs have sagged to the point that the frame is riding on this cushion, that could be part of the problem.
Also if your original shocks are worn, they will not dampen the suspension travel when a bump is encountered.

You're certainly not alone! Google "W24 chassis handling improvements" and you'll get a quite a few posts from folks in the same "boat" as you...and yes the improvements and fixes are there too. I believe you can have the springs re-tempered so they become "springie" again. Good luck!

First would be to weigh all 4 corners of the coach as loaded for travel. Then adjust the air pressure to the proper amount for the highest weight on each axle. That would be the first step and cheapest before throwing a lot of money into it. My '03 runs with 90 psi in front. It is a 3778 model so close to yours.

If you are correcting all the time as you go down the road, chances are your front end needs to be aligned. All 5 of my coaches needed an alignment. Find someone in your area that does heavy equipment. Find out where your county gets their trucks worked on.

105isp sounds very high. I run 90 or was it 95psi in the Hankook tires? Koni shocks made a world of difference. Safe=T-Plus is also a good investment I have found.

I hope all this helps some.