What percentage should go towards my personal mortgage, toys, travel, etc..Further, I wouldn't want to develop spending habits that had me on razor thin margins, so what should my OVERALL spending percentage be relative to my cashflow?

A good window contractor could replace your whole job in a day and charge roughly $125-$150 per opening (in CA) which includes hauling away the old sashes and caulking and weatherizing the replacements and trims.

I am toying off and on with switching over to the Master Landlord locks but I don't like the expense. 

And I get new ones delivered free or low cost (and the old one hauled away). 

The reason is that over the long haul I expect market rents to go up 1-3% per year along with my expenses.

Often there is nothing needed...but, yes, occasionally a unit will need rubbish hauled out and repairs, but these are the exception, as far as Tenants I have placed.

I’m looking to build generational wealth so I’m in this for the long haul.

When they leave, they can take their toys and assets with them.      

I have toyed with the idea of using the '12 month buyback guarantee' but don't know if that will get me much ahead, unless there is just some bad fundamentals with the location of the house. 

We've even toyed with keeping the house as a furnished vacation rental on VRBO, AirBnB etc. and using the 4-plex capital to expand our investing capabilities.