About your house sitch with the down payment being a loan or a gift. I have been down that path. My father claimed an interest in the home that I was selling to stop the sale of the house.
But it was a house that he had agreed to purchase and signed off on financing condition and it fell through, I stepped in and bought the house to live in, I was approved for the mortgage and my F gifted the down payment. The L drafted a paper that stated it was a gift for the bank. F did not sign it the L did acting on his behalf.
With the failed agreement of purchase of sale my F was able to convince a judge that he had interest in the house and a lawsuit was granted. He claimed that I was holding the house in trust for him until he could take over the payments. I was living in the house for five years before this happened.
After a short battle and much expense I lost the house. My parent lost me as a son as well.
My point is that you are right, if they decide to take you to court you could loose the house as it might not be worth the fight to keep the house. As was my sitch.
Me late 30's W mid 30's T 15, M 10 S4, S7 ILYBNILWY June 2015 In house S July 2015 W rings off Oct 2015 My ring off Feb 2015 Separate houses June 2016