Am I over the Max 5fer length?

Although some states have the 40’ trailer limit, I don’t remember any one saying they were ever stopped for trailer length. Overall length yes, trailer length no.

State, National, and local campgrounds can be a problem even at 35’+.

I have problems with just 34'.

Full timing in a 42' Alpine. Zero issues, even in small campgrounds.

After reading thru the article you posted...
1st - is that really from 10 years ago?
2nd - it appears that most of the 40' restrictions are for trailers. Not sure how anybody would treat a 5th wheel, and can't imagine the authorities would care.

I have been pulling our 42' fiver since 2008 with zero issues.... The only campsite we had issues with was a state Park in Florida...

no, You will be fine pulling the trailer assuming you have a proper set up. Finding sites in state parks is the biggest issue, especially in the west.

Legal length won't be anywhere as big a problem as finding usable camp sites!

At 35 feet I have to watch for short sites, particularly in Government CGs.