While echoing everyone else(you can't afford this, it's a financially stupid decision), if you are deadset on being stupid at least you are doing your shopping.

Check your local credit unions. I just spent the last month rate shopping for a used auto and found a local CU with surprisingly great rates for used autos and pretty decent rates for RV's depending on year of the RV, starting at 3.6% for <10yr old RV's and 6.9% for >10 year old.

Your credit score is going seriously hurt you, also your DTI likely implies long loan which usually means higher rate. You are basically in the worst position possible for RV shopping, at a shitty time to be RV shopping.