A few thoughts for you:
If you sold the house, what type of a property would you replace it with? Given the knowledge that you now have, what would a perfect rental property(s) look like in your market? The point of the thought exercise is to separate the issues of financing from the ownership of the property. In other words, do you have just a financing issue or both a financing and property issue. If you think you might have a property issue then sell and replace with a better property. Just remember that buying property in this market is difficult, and there are costs involved. As a side note, if a rental property is merely covering the costs of interest and operating costs then it would not be profitable enough for me to hold.
Generally speaking, I think a 15 year mortgage is a bad choice for real estate investors. (My personal opinion). It ends up using your cash in a very non productive way. Your money is tied up in equity in your property that is hard to unlock. We try to use as much of other people's money as we can to finance our investments. Our banks here in TX give us 5 year loans with principal repayment amortized over 25 years. I'd look at your options to refinance the loan. Sometimes you can go back to the bank and ask them if they will modify the amortization schedule. Just remember that rates are rising so a refinance will almost certainly cost you more money. The other side of that is that a 3.5% loan is a nice asset to have with inflation running at 8%.
Lastly, you did not mention whether you have the option of raising rent. Generally, landlords pass along rising costs to their tenants. You've experienced rising costs and you should pass that along.
Overall, given my limited knowledge of your situation, I'd lean towards selling. If this was a great rental property then it should be throwing off more cash than it currently is.
Good luck!