One day I would love to own a mini storage business. 

They also will not help you with your living expenses, it'd be nice but that's just life, they are a bank.If I were in your shoes I'd be keeping in endless contact with the current lender.

Other ways to increase value would be to find places to cut or lower expenses (laying off bad maintenance or property management or renegotiating cable or landscaping services lower or even taking water or other expenses and making the tenant pay for them if that's common in your area) and finding ways to add income besides raising rent (putting in vending machines or coin laundry, storage units or parking spots).

The basement is going to be cleaned up, but not finished entirely, mainly used for storage.

You make a seller believe their property is sold with a bogus contract and they may well carry on like they are selling, that means moving things out, getting storage, contracting on another home, travel expenses, the list of activities goes on as to what a prudent seller may do and the costs they incur. 

Looking back, what is the next step you'd recommend someone in my shoes taking?

I've heard ideas such as adding storage space, renting furnished apartments, raising rents by percentages annually, wholesaling cable/internet to tenants, etc.  

Commercial brokers specialize in asset class and deal size.For instance you mentioned locations already so ( example: self storage facility 100 doors or more at 5 million and higher minimum 7 cap,etc.)The more descriptive the better usually.

When you are ready to retire for sure, then cash out for cash flow properties.Personally I'm starting to lean toward renting out RV storage.

Put yourself in the seller's shoes.