There are two problems here that are only partly addressed.
Did you notice that both the MI people were saying that your insurance should deal with it? That is only true in Michigan and the other "No Fault" states. (It is also why Michigan has the highest insurance cost in the nation.)
It is true that in most states, the "at fault" drivers insurance should cover you. That is if the other driver even has insurance. Either way, with a custom RV you are in a bad place. You can try to find someone knowledgeable to write an appraisal based on the "before" condition as assumptions. That can be hard.
The other issue is "Total". The fact that the vehicle is called does not mean it has no value. A "total loss" just means that the cost of repair will exceed the cost of replacement. If there is no replacement, then this point is moot.
Those of us (like bsinmich) that have classic coaches go with an appraisal and agreed value. Few companies still write AV policies and they are not cheap. But, if one of our coaches gets hit hard, we have a good chance to recover a good coach when everything clears up.
Matt