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Congrats of fighting off a terrible disease. The FICO 9 scores apparently are not going to count medical collections against you but I don't think any lenders are using that version yet. I would apply with the lender you have a history with, I am sure they will approve you. Let us know how it goes.
Sorry to hear about your health issues, you are a survivor! Looks like you're looking at a Mazda--so am I. Cap1 auto navigator is pretty lenient and I just approved at NFCU with mid 600s. If you are trying for Penfed they can be a bit conservative but for auto loans they are looking for 620 and an otherwise clean report.
Which CU are you thinking of app'ing with? Also, have you tried the WhyChat method of disputing medical collections?
With 20% down you should be able to get a fantastic loan.
Congratulations!