Mortgage costs and tax are complicating our move

My partner’s CGT liabilities from selling his rented property plus divorce-related debt may leave us little for a new place – have I got the numbers right?
Q I am writing in utter despair and I am hoping you can help. My partner owns a house that he has always rented out. He now needs to sell this property so we can buy our first house together as we are currently renting. He also needs to clear a debt of £50,000 from a messy divorce. My partner bought his rental property in 19