wip, the Verizon 4G card should revert to 3G automatically when 4G is not available. You mentioned which you had 3 years ago, it should have been 3G, providing you were using a Verizon data phone, or a Verizon data modem.
To answer your question about Verizon in the lower 48, just like all the other carriers, they lie about their coverage. Their coverage maps are apparently a wild a@%ed guess. For example I can tell you their map shows solid coverage in most areas in Texas, yet even with the map showing excellent coverage it's not true.