I can't answer the question why the installer did what he did. If you have a complaint about that it's best handled with Verizon Customer Service, rather than through this peer-to-peer forum.
However, since you do have coax already running to the room where your computer is located, and if (this is important) your Actiontec is being fed by coax now, the amount of work involved in moving the router would be minimal. Just disconnect it from it's present location and reconnect it in your master bedroom.
You may need a splitter for the coax in the bedroom but they're inexpensive and easy to obtain.
If your Actiontec is currently connected to your ONT via Ethernet, moving the router would still be done the same way but you'd then have to call tech support and get them to change your ONT's provisioning from Ethernet output to coax.
Once the router is moved, connect it to your PC via Cat 5/6 cable and in all likelihood you'll start getting the full speeds you're paying for.