House renovation - Cost & Contractor payments

Hello, I had my existing house renovated, a new kitchen constructed and redo of doors, windows, floors and minor repairs like paint, grills. There was a deadlines set up, emphasis on quality construction/work, and basic payment agreement for a reasonable scope. Contractor missed deadline by 1.5 months, showed bad quality of work ( water accumulation in roof) , bad finish in several areas and refused to follow standards for safety like electrical wiring. Requested payments done per agreed plan &schedule without delay. Final payment was only after all requested work completion, final walk through and sign off with me. Work remained unfinished on roof correction, grill stability, etc., deadlines missed 3 times and contractor did not follow my instructions. Contractor is now asking for huge & final additional payments without showing receipts, or break down of labor, material and commissions for any work done. Contractor refused to acknowledge delays, water collected in roof during rainy season, bad quality work. Contractor file police compliant, and is now threatening civil suit. Can you advise the next step ?