I know rents have increased dramatically over the past two-three years but do not count on it continuing.

Only way you can boost your ROI to acceptable levels is to somehow put less money down (add partner or more leverage) which may be too risky considering it is your first time deal.

So, I figured a refi is a way to get the lower interest rate and boost the credit score back up. 

According to a  survey, it is seen that there is renewed interest in residential investment properties, thanks to upbeat real estate market in 2015. The factors which have caused the increase in residential market are...

But there are rumors the area may get a boost from a cracker plant bringing some jobs and certain retail chains recently moving in like the petsmart in union twp.

If you go about 8 blocks to the west, there's a dramatic transformation - it becomes indistinguishable from Braintree.  

What @Bram Spiero is alluding to is that if you had that  house leveraged to the hilt with little cash of your own in it your cash on cash return would be dramatically higher - but so would your debt.One other thing to consider is that right now you can sell that house and the profit from it would be tax free because of the sec 121 primary residence exclusion.  

.$400k x %20 = $80k down payment to close (ignoring closing costs and repairs) Now its up to you to figure out the expenses of the deal, including your mortgage payments. lets say if you are renting for $3000/ month, its not unreasonable to assume you could take home $1k per month after expenses (I am simplifying dramatically for time's sake).$12k gross for the year on a $80k investment = %15 cash on cash in the first year if everything goes perfectly.

I ave worked for lenders that can do a 56.99% DTI on FHA loans.To boost your credit score I recommend wiping out the credit cards first.

Many are reluctant to dramatically increase that appraised value on a SFH  within 1 year.Are you talking about a single family home?