I'm in the same boat as OP, great advice in here.

Those first two exculpatory clauses the OP mentions would likely be voidable and thrown out in court if challenged under most states rental laws instantly.

And as to my op, to get hit with a 7 figure settlement, I've got to be at fault.  

The way you react to things determines the goals you set and how you reach them.Think about working from a co-op space instead of from the kitchen table.

OP  curt is a knowledgable local broker who owns a bunch of rentals himself..  

I hope some of you who have experience dealing with co-ops and their management companies (especially in NYC area) can give me a hint how deal with the management company who for years deliberately makes my life difficult and put unnecessary burden on me and my investment.

The OP's question is whether it's appropriate to value it using the broker's proforma numbers. 

There are some lenders that will do HELOCs on co-ops but again, your co-op will probably have to give approval.If it's not cash flowing great then it might not be a bad idea to sell and get into something with a better return.

I gather the Co-Op is offering this financing?   

Marcus Lemonis has a TV show doing what the OP posted; read the biography section of link below to see how he started:https://en.m.wikipedia.org/wiki/Marcus_Lemonis