First, how would they know you were towing overlength--are you thinking about being involved in an accident? Insurance is not 'voided' because of stupidity, they would handle your liability, but might not renew it.
As to the specs you have listed, don't think I have ever seen one that would meet all of them. Shorter fivers tend not to have standing room in the bedroom...
Might look over RVTrader.com for some listings/PPLMotorhomes.com also, to see if anything is out there.
And, welcome to the forum.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired