I agree that the 110 is the best solution for you.
This unit was designed to sit between your phone and the phone company. You could siphon some or most calls off to a voip provider yet still allow 911 calls and other combinations of local calls to still go out through the phone company.
In your case you would use the box to pass 911 to the phone line and have everything else go to the voip provider of your choice.
If you call 911 and they call you back, those calls come in through the phone line to your phone. Voip calls from others also come into your phone.
Early models of the 110 had a physical relay in them so that in the case of a power outage at your house, the 110 would look like a hardwired connection to the local phone line, ie transparent.
Later models eliminated the relay and leave you with a less than dsireable solution of having to remove the 110 and plug the phone into the phone line during a power outage. (I posted a diagram here years ago showing one solution that people could build to duplicate the "power out/ connect the phone to the phone line" issue.