Would love to get that lower but some quick googeling says that Republic Wireless is less than happy with users tethering. Is this true, are there better plans that allow tethering?
First, I'd recommend reading
the guide if you haven't already (not sure if you have or not - it's amazing how even some of the old timers have missed the sticky at times).
As to answer your question specifically, tethering with Republic is a colossal no-no. In fact, you'll find tethering with
any carrier that offers any sort of "unlimited" data package, the tethering issue is against TOS. The way the industry is rigged, you're not going to find much in the way of tethering options for less than what you're paying right now.
Airvoice technically allows tethering (no forbidding of it), but they also have fixed data allotments and you have to activate the other half of your data after using the first half. It's not that big of a deal because it's only data (OHS NOES! I MAY BE UNPULGGED FROM TEH INTERTRONS FOR UP TOO TWELVETY BILLION HORUS AFTER SENDING SUPPORT AN EMALE!!!!111!1~), but you'll find the occasional complaint about this anyway.
Basically, so long as you can find a provider that does hard capped quantities of data, you can tether. Unfortunately, there's no many options outside of expensive per megabyte PAYGO options or basically "unlimited" talk and text with data plans from Airvoice/Jolt for yourself... and paying $40 or more a month anyway. This said, Red Pocket does do a T-Mobile based data only SIM, with rates starting at $10 for 1GB of data per month. There's also outfits like FreedomPop or NetZero, if you don't mind the datamining and the slippery billing practices... but that also means another device to carry around, and it's the Sprint network.
The cold hard truth is, mobile data is expensive, and the mobile companies want to gouge you out the wazoo to permit you to use that data with anything but your mobile device itself. That's why I just advocate what I do.