Sorry about the wall of text, and I apologize for all the if statements in this post... This certainly seems like a line issue and not a router issue, but save your ISPs tech support some steps and do this:
MOST ISPs will get out of doing anything they can, especially if you have a router connected. The best thing to do, is connect your modem directly to one of your computers (you'll have to powercycle/reset the modem after doing this), and running the speed test that way. If you still have a slow speeds issue at that point, something is definitely wrong with Verizon's modem/line. The other thing is, you switched from a cable provider to a dsl provider? (I know Verizon actually offers cable service in some locations...) But what I've found from working in the ISP industry is that sometimes you may have better signal reliability, or be physically closer to the ISPs equipment with cable or dsl (one or the other is typically better for your location).
After connecting your computer directly to your modem, run a speed test, if you have the same issues DEFINITELY call Verizon back for support. If you can't get any assistance still (while the router is bypassed), ask to speak with a supervisor, they will probably transfer you to higher level technical support instead. If this person still cannot help you, make sure to ask if there are any minimum service guarantees (some companies will guarantee at least a basic level of service), bringing this up may force the technician/service rep to actually do something. If/when you do get a service call to your location, or possible NOC (network operations center) issues have been checked, your speed issues should be resolved. You may need to throw the 'cancel' word in every so often, or threaten one good time (obviously threaten to cancel)...
This should help you out in most situations, if not then go back to comcast.