Incentizes the listing agent to find a buyer and the seller to accept it.If buyers will have to price match/comparison shop between the different fees, it just becomes a small nightmare for them.

I am talking about a legal insurance company that would write a policy that a lender would accept.

You don't have to accept section 8 as far as I know, thankfully.

I was able to get the seller to accept my price near what they were asking .

I do have a friend who does 12 month leases for each bedroom in his investment single family homes and a lender will accept that rent.

Probably an extra clause in the lease should be added in the future to insure the tenant accepts the property as is when it comes to these internal elements.

Are there lenders who would accept less than a 20% DP or is this an absolute must? 

They might be hoping that people will just accept that and pay it.A year in a new property is not very long so the place should not have much wear and tear or cost to turn over. 

Is is acceptable to claim the hours if I'm managing the STR remotely?

Only issue is they are only accepting cash offers.