I'm going to get this wrong because I haven't had a chance to give it a lot of thought, but here goes.
1. We're pretty confident that Eric was involved in more criminal activities than just blackmailing Chris and Steve.
2. If Eric was in cohorts with the Piedmont sheriff, we can be pretty sure that he'll blackmail the sheriff with the threat to reveal everything (why wouldn't he?). So, I'm expecting Eric to be released, get a slap on the wrist, or is found dead if that was the case.
3. We are uncertain as to whether the sheriff was aiming at Chris or the jeep. If it was the former, then he must believe Chris has some seriously incriminating evidence against him. If it was the later, he wanted to apprehend Chris for questioning, probably in some backroom somewhere.
Are the sheriff and pastor working together at all? It is certainly possible that they aren't, but given that it has been stated that there are other gay couples who are out, having the pastor target only Chris and Steve is suspicious. It could be explained on the basis that Steve's dad is a cop and hence implies that the law enforcement in their home town has been 'corrupted', but I think it's likely its because the sheriff wants some sort of pressure applied -- maybe just to discredit Chris and Steve if they come forward later with evidence against him.
What sort of criminal activity are they involved in? I'm going for something basic -- embezzling or drugs. I don't see any reason to go for something extreme -- those two are common enough. Of the two, drugs would be more likely if Eric has become involved. I can't see how he would get to learn about embezzling in another town, BUT he could have learnt about drugs being pushed.