VOIP isn't really a very important feature for me since I don't talk on the phone very often, and when I do plan on having a longer call I usually use skype.
Okay, I think you're approaching the problem a bit backward, and you're making it more complicated than your entire setup really needs to be.
First, you'd be surprised about how much of a delay not properly poking a hole through a router can cause with voice services if the app or device isn't keeping a hot connection open... but this is besides the point.
Now, have you tried
the guide (
unabridged) yet? Are you familiar with my
write-ups on
VoIP service?
The bottom line you need to consider is if call reliability is important, GV really isn't the path that you should be taking. This said, if you're insisting on only one inbound phone number and keeping GV, you might want to consider forwarding 100% of those inbound calls to your mobile number instead of just relying on VoIP through Hangouts as the call forwarding/global call hunt is far more reliable for receiving calls than what you have currently. This is where having another open standards VoIP service with an inbound phone number comes in handy, either by using an ATA or a SIPphone app. This would let you do all your calling on real phones instead of trying to piece together a plethora of non-compatible proprietary communications apps.
Give the links a read and think about how best to optimize your setup for the money, and bottom line, don't be afraid to pay for what you actually need.
Best of luck, if you have any further questions, let me know.