This painter previously corrected a poor drywall installation of 2 walls and painted with Sherwin Williams small drywall, which looked  good to my untrained eye.  

Lastly, when i try and call them to speak to my property manager 99% of the time I wind up having to submit a note in their portal and wait for a call back.As to to the new garage door that will be installed by the tenant, I wish they would be more involved, giving the tenant some options of companies to call, and to walk them through the repair process.Am i wrong in any of these thoughts or concerns about my current PM---or---do i need to let the property manager do their thing and learn to take a step back?

He will know if the heater is even installed correctly, safely, and to code.

If it cost you $5000 to install, use that as your starting point.

If you had a default interest clause in your promissory note and didn't enforce that and they still made monthly installment payments, for which you accepted each time, then you are in a sticky situation to require additional extension costs. 

Installing a GFI at the top of each circuit is ridiculously easy, as you say.

Cutting tiles can be a challenge if you have angle and corner pieces but a basic install isn't too hard.

Insulate, add electrical, mini-split ac, and possibly plumbing, as desired, drywall, tape and paint, put built-in cab's on one side if you want, hang the tv, speakers, etc, install bi-fold/multi-fold doors on the side leading to a patio, and replace the garage door with an insulated one keeping the track and removing the motor, or install a carriage type garage door into the existing garage opening.

It involved installing meters inline that reported wirelessly to the internet and allowed you to bill each tenant.  

Here is the specific language from Assembly Bill No. 68:a local agency, special district, or water corporation shall not require the applicant to install a new or separate utility connection directly between the accessory dwelling unit and the utility or impose a related connection fee or capacity charge, unless the accessory dwelling unit was constructed with a new single-family home.If the Planning Department is telling you that you need separate utilities and you're adding an ADU to a lot with an existing SFR, refer them to the above language from AB 68.