I like to pre-screen and determine upfront who I am really wanting to work with!

My question though is how do they determine what is  considered multi family and what is not?

This may be a matter for legal counsel and financing source since you will have to determine how the funds are transferred and who will ultimately "own" the property & building(s). 

This will help determine how much "wiggle room" you have. 

I didn't have insurance so no reimbursement there but I would think FEMA grant money received would at least be considered a partial reimbursement.How do you determine the amount of the loss? 

I’m trying to determine the best course of action to take for buying a residential property in Florida with my current situation (information below).

There could be value in approaching an owner of a tax delinquent property prior to the tax sale if you researched the title and determined that the property actually had some equity in it.  

My question is how do I determine the worth of the lot if I sold it to be used for this purpose and who would I sell it to?

The cost to build will also be a determining factor. 

I like your determination!