Flying LV → Boston → Dublin

Flying LV → Boston → Dublin and back on 1 to 7 may, and I have a few questions:

1. On the way to Dublin (layover in Boston ~1.5 hrs), do I need to go through TSA/security again or can I go straight to my gate?

2. On the return (Dublin → Boston → LV, ~3 hr layover), where do I go through U.S. immigration and customs—Boston or Vegas?

3. I’ll only have carry-on bags—does that make the process faster or change anything?

4. I’ve heard about U.S. preclearance at Dublin Airport—if I do that, will I still need to go through immigration in Boston?

5. I’m a U.S. citizen, but I’ve heard scary stories about ICE at airports—should I be worried at Boston Logan?

Would really appreciate any recent experiences, thanks