Here's the problem you face, Colgate: As of right now, no Verizon MVNOs support LTE devices (this may be changing very, very shortly... like in hours shortly), this means (right now) you can't take your Verizon iPhone 5 to a Verizon MVNO. Once LTE comes however, there still might be an embargo on
which iPhone handsets can be activated, so don't entirely put your eggs into this basket... and just keep the option in mind and keep an eye on the Page Plus and Selectel websites the next week. Even still, it probably wouldn't do much for you financially without working out some way of
going on a bit of a data diet. If it's tethering that drives some of those numbers, it will complicate things and limit you in your alternative carrier choices.
I understand the whole business angle, but the biggest burners of data is media like streaming video and audio, and GPS... the great news about the GPS issue is that there are offline GPS apps available. The rest is just trying to eliminate as much personal data usage as possible and keep it business only. That's not a bad thing, however. It kinda sounds like you really need to start to separate your personal life from the phone anyway. Let it just be a tool for you.
Now, a great thing about the Verizon iPhone 5/5c/5s: the SIM slot is carrier unlocked for US GSM providers as per Verizon's LTE spectrum purchase deal with the FCC. This means that your phone can be taken to any AT&T or T-Mobile based MVNO that strikes your fancy and meets your
needs. Given the fact that prepaid GSM service is cheaper (especially on the data end) than CDMA, even with the pending LTE device support and service, it might be more worthwhile to weigh your options on a different network. AT&T's coverage is usually pretty thorough, but some areas, T-Mobile has better. Just check coverage maps and ask a couple folks.
You can do this without replacing your phone or doing wasteful switches just to stick with CDMA service... and if you can keep your data usage in check (under 2GB - or could survive with 2G data throttling above that point), you shouldn't have to spend more than $50/month. You eliminate the heavy data dependence though, you could get down into the $30 or less range. Hope this helps!