If your televisions are also bringing in satellite feeds, there should be a function in your satellite receiver for you to test how accurate the alignment on your dish is. If it's an older installation and the alignment has changed slowly over time, that could account for poor Internet speeds, although weather conditions certainly don't help.

I've done this before. It takes two people communicating by radio or cell phone, one on the roof adjusting the aim of the dish and the other one inside watching the signal strength meter on the receiver. This needs to be done on a clear, sunny day with no clouds at all.

Verizon is a valid alternative but read the contract closely for data caps.