You are also paying him more than you would a professional management company - most will find tenants for you for one months rent and then turn over to you to manage if you like (not MORE than one month rent typically) and they know what they're doing.  

Is this typical for such old properties, or excessively high?

Minimum ratio depends on the lender but typically it is above 1.0. 

asking all the veteran STR owners/managers. what are the things you would consider including in new construction being built for STR?

Typically I pay it, no questions asked, because why would I have any questions? 

Even a postage stamp sized patio or yard can be very attractive to midterm guests.Do you typically rent your ADU to traveling nurses?

Typically a seller will not close until the funds are in escrow.

For newly constructed, purchased or renovated properties and also retroactive generally over the last 10 years, building components are properly classified into individual units of property and accurate recovery periods for computing depreciation deductions.

I know that I would also need to qualify for a construction loan to rehab the property.

I don't know many urban/inner city new construction residential projects where the Code doesn't require sprinklers for life safety.