Absolutely cannot reset my Moto G 2nd gen tracfone
I have the EXACT same situation (had it since Christmas, had all the same issues you listed when I updated to Marshmallow, and my mom has the same phone and factory reset hers with no problem). I just did this so I'm not sure if it's just a quick fix, but I got my notifications and lock screen back (home button still doesn't work though). 

Go into settings and click "users"
Switch to your guest user (if you don't have one set up, you can probably set it up) 
You should get any notifications that are for the whole phone (ie if there is WiFi available or if your storage is close to full; app notifications shouldn't come up)
Go back into settings>users and switch back to the owner account on the phone. 
Your lock screen should return, along with any notifications you missed. The drop down settings menu is accessible as well.

Like I said, the home button is still unresponsive for me, and I'm not sure if this is a long term solution, but at least it's something!