I would assume you spent extra money on this mirror so you could attract and keep a quality tennant and would hate to loose out and have to pay to have a vaccancy and find a new tennant.  

I would imagine that in your part of New Jersey, the extra income would be significant (maybe 12k per year?).

Personally, spending the extra money on a home warranty for rentals is a waste of money.

You might have a few dripping faucets and a toilet running occasionally costing you a few hundred extra per month.  

Do I care about the extra interest that will not accumulate or do I care less because I can acquire another property and someone else is paying the interest?   

If you have extra money to give away, I guarantee I can find charities that are in greater need than your tenants.I also disagree with small increases over multiple years or even over a one-year period.

meet with a lender and go thru the formal pre approval steps to know for sure ..if the 15 yr fixed payments dont work for approval - fall back on using 30 yr payments ( and then just pay extra to payoff the loan quicker)  

It took a little longer than expected, but totally worth the extra time.

In addition, should I pay the extra 600 to bring the rate down to 4.99%?  

Rents should try to reflect any extra costs you incur so long as the rent remains in line with the market rate.