Help with car decision

Hi, I am going through a separation. He is offering $33,000 for our car, which I currently have and need for work. We bought it last year for $28,189. I used an online tool for my car and it says it is worth $20,000 today. The problem is, he knows I need it and am used to driving it and would prefer to keep it. I have emailed the nearest dealership (1h away, so not easy to get to) and they will have two similar vehicles next week, one for $31,000 + HST and one for $32,000 +HST. Both are 2 to 3 years newer and have less mileage. There is lots of competition for these cars so I can't guarantee getting one. I would like to not accept $33,000 as being the value of the car, even it if gives me more $, and keep the car. I would like to insist on $20,000 as being the value of the car and keep it. Am I being ridiculous? TIA.

Thank you Itsnicoma for explaining to me clearly. Thanks everyone else for taking the time to respond.