It is safer, cooler, and lasts longer than turf sold just a few years ago.  

A structural engineer is your best bet.

Personally I'd imagine going conventional or refi conventional and another FHA will be the best bet though.

I think the best bet might be to finish up with the current GC.

Suzanne B. there are a couple of steps to consider:1) Removal of the old radiators, pipes, and boiler (I've repeatedly (3 times) had this done for free by people who want the scrap)2) Installation of the furnace, trunk, and plenum (five times, cost of furnace plus $1k in labor/mats)3) Installation of ducts (depends on the type and length of ductwork needed, put I bet in your case it won't be too crazy)4) Installation of returns (same possibility as #3)In my experience ... for #3 and #4 it depends a LOT on the layout of the house, and how often the people you hire have done the work.  

But your best bet would be to find something already zoned for multi family.

What are some of my options or is waiting it out rather than spend any more money on legal the best bet ? 

This would be much safer if it does not go as you expect and it would preserve your down payment cash for business operations & growth. 

In general, the more documents the lender can provide in court, the safer they feel about the paper.

You hedge your bets with multi family because the likelihood of all your units being vacant is low.When a single family property is vacant not only is it not making money, it’s costing you money because of  scheduled monthly costs; water, insurance, utilities, mortgage, property management fees, etc.Scale up with multi family , it’s the better play.