Is it possible to pool enough money to finish a small portion(special purpose to lease to gain capital to pay to complete it), that would compliment your original use? Given you are looking for it to be a wedding venue/corporate event, I am thinking taking approximately 1000-1500 sq ft and have it built out as a catering space, rental commercial kitchen? Bring in a large refrigerator, commercial ovens, etc for 25K and start leasing that portion to a catering company that would directly benefit from your intended use, as well as provide positive financials to a lender... I always try to get creative while viewing the overall "big picture". Maybe bringing in a portable stage, and portable bar for private events and parties. I wish you good luck. Tough position to be in.
One last question, did you have a 10-20% built into the loan to allow volatility in the market, supply chain issues etc, and if you did, did the GC blow through that? I would have boots on the ground counting every nail, every board to keep the guy honest, but I would have been that way from the beginning, so he would know that I was watching.