Expanding and monitoring dumb system

Good Morning,

I am looking at replacing my Smith Thompson (monitored) DSC 1616 board with Konnected and pulling all the hardwired window and door sensors into my existing Smartthings. I have a few questions:

I have two wireless glass breaks added by Smith Thompson and they communicate back to the main box via a small wireless module they added. Can I do anything with this or are those two sensors a loss?

I have 8 interconnected 3-wire 120VAC smoke detectors. So far I've found that I can either run some wiring through the ceiling (not easy) and ultimately connect them to Konnected via some relays and modules, or I can rig up a relay and a window sensor to get them to activate in Smartthings. Am I missing another option?

If I sign up for monitoring (Noonlight) - are they monitoring Smartthings or Konnected?

If I want to start adding my own sensors (motion, etc.), is the idea to get Smartthings-compatible sensors and add them in Smartthings or do new sensors need to wire into Konnected?

Any good 3G options for monitored systems?

Thanks a bunch!