Throw out the high-value outliers. 

But you don’t need a new lease to make a security deposit amendment, that’s just a one page amendment.

It sounds like you’ve got a solid plan in place with the bank refinance to secure long-term financing.

Yes, you can deduct the 8 days rent from the security deposit.

Most tenants pay using secure ACH transfers from their account to mine.

Although there is no way to prove this, (I reside in FL; the investment property is in AL) my GC tells me the unit was secured by a cage and bolted down.  

I'd look into sound reducing alternatives before you throw the baby out with the bathwater. 

Don't forget to tell the tenant where you will store their security deposit.

Operations and Security Deposit accounts

Not just you throwing bleach on it and painting over it.In general it sounds like you were notified of the issue, attempted to correct the problem but were unable to due to the tenants non response.