Perhaps your #6 of repurposing commercial in to multiple small residential units is the best idea I can see in SA as it has had way too many Single Family rental homes added the last few years. 

I recently added a half bath were half bathrooms add $50k of value

He's done everything on my list but adding the bathroom in my basement.

Echoing some of the comments from others on this thread and adding that the LLC is purely for asset protection and limiting your personal liability. 

Possibly but the problems I’m having stem from having too many cooks in the kitchen already so to speak, and failures of what is supposed to be seamless transitions among different payment systems, so I’d be worried that adding another layer of complication, more entities and more software could lead to more potential failure points.

You can use bat insulation or spray foam, which has the added benefit of giving you an air-tight seal and also keeps the bugs out. 

We use Propstream but I am looking for some added info that Propstream does not easily provide  @Sean OToole is the owner and he has built an incredible platform..

However, I should note that this tenant has been late paying rent several times recently, which has added some strain to the landlord-tenant relationship.How would you approach this situation?

First of all, I suggest you search the forums as arbitrage has been discussed ad nauseam.

In fact adding unit to SFR in area with true zone MF also seems to not get the negative impact from adding an ADU.