Using insurance check on stuff other then my car?

As long as you don't have a lien on the vehicle you can do whatever you want to with the check. If your insurance co finds out, they may not want to extend full coverage on a vehicle with prior damage. I don't necessarily agree that this accident was your fault. I have handled multiple claims where a vehicle pulled out in front of our insured, who swerved to avoid and struck a parked vehicle and they were not at fault.