Battery Doctor worked for me! In its prefs, I just selected "Disconnect Data Radio" with "On Power Off" and left the other prefs unchanged.

This app, combined with unchecking the "Automatically collect messages" default in the MMS preferences, gives me complete control over my data network access. I also downloaded the latest SnapperMail, which now allows for "Attach from Media"; the Media app forces sending from MMS only, which has additional costs.

I really believe Verizon is trying to force customers to buy its $50/month data plan given all these hurdles.