I'm voting to KEEP THE CAMPER!
Sounds like you've devoted a lot of time and money building it up to exactly what how you like it and it would be such a shame to see it go.
How long would it be before you could afford to buy another?
My philosophy is to never sell a toy unless a replacement is in the shed or on its way, i learnt this lesson the hard way when I was into bikes and got rid of them and it took ages to get the wife to agree to spend the money for a new one. Riding was what I loved doing and I cut myself off not realising how much I would miss it at the time.
You'll have 30 YEARS to pay off the house, is the plan to do nothing in that time and just put every cent into paying off your mortgage?
Maybe another option is to sell the camper and buy a cheaper one?
Don't forget you've still got to live your life and enjoy it along the way,

My 2c
Hope this helps.