Understanding MoCA

I've been going in circles with Motorola's support regarding the MM1000 MoCA Adapter I ordered. It's unclear whether it's going to work with my house's configuration, and so I'm unsure if it's worth the risk of ordering a second one. 

1) Point of entry of Comcast cable into house is unclear. Numerous Comcast techs over the years have been mystified as to where it is. Luckily it all works anyway, as long as I don't need wired internet downstairs.

2) Oops, pandemic happened, and my wife needs wired internet connection downstairs because she can't share the office with me due to confidentiality requirements.  So I'm told I need two MoCA adapters. The first upstairs coax > MoCA > modem router. But I don't understand how that will affect the cable downstairs. Unless it works that the MoCA then sends the assigned IP address internet signal back into coax, and throughout the house network?

3) Coax downstairs currently going into DVR. So I'll need to plug it into second MoCA, then to DVR, and then I can run the ethernet connection directly to the laptop downstairs, fingers crossed that the coax network is all connected. But it all must be, because it's all the same Comcast service, stemming from one single coax cable coming into some mysterious point of entry. I'm told that's the only way to get internet down there. Though technically if I had to I could simply put the modem/router down there.

Thanks for your help.