Sub-panel ground and neutral connected to main ground and neutral bar?
First you don’t add the amperage totals that way. 
A single RV has a load requirement by code I think it is article 551 but this is an old code book , 9600va at 240v is the required RV supply for a 50 amp 240v service. A single unit requires 100% . Yes I have had a larger feed on a large RV with dual ac’s , after downsizing I am back o a 30 amp 120v (single ac) on a 30 amp breaker as required by code.
So look at article 551 in the national electric code, would I upsize my feeder with my last big class a yes I did. But not on my small one that I have today after the kids left.