There is definitely a lot here that is YMMV. Depending on who you finance through and the vehicle you are looking at many of these factors can be detrimnetal to the loan approval or have minimal impact.
The biggest thing hurting an auto approval is your lack of previous installment loans. Banks are always cautious about lending large amounts of money to borrowers that have never shown experience with that amount of money.
Question #1 - POI may or may not be required depending on the lender. WIth your scores you whould qualify for a top tier, which usually doesn't require POI. However, your lack of installment loan history will most likely send the loan request to manual review and underwriting may require that you provide POI.
Question #2 - This also varies from lender to lender. Most will use the YTD on your paystub to calculate the anticipated income for the year. I have seen excepions to this where the lender will use the hourly pay rate and the average hours worked over the last 2 paystubs and calculate that way. One thing to note, most lenders will NOT include overtime pay in their calculations when proving income.
Question #3 - I do not have experience with this, so I am not sure. I know alimony and child support can be counted, but they don't have to be reported. If it were me, I would include it in your income and see if the lender even asks for proof.
Co-signer and Co-borrower are the same. I would apply by yourself first and if there are no approvals you could try adding a co-signer. I have seen co-signers hurt and help. Of note, many banks require the co-signer to be a spouse, parent, grand-parent, or child. The less direct the relationship the less likely the bank is to approve of the co-signer, this could be especially true if they live out of state and have subprime credit.
