Where can I get help planning my plane trip?

The connection time westbound is a bit on the very short time. You have to get through immigration, get your baggage, and then tramp to the Jet Blue terminal (the last one is not such a big issue, as the AirTrain is very quick, and operates frequently at that time.

However, you still only have 2.5 hours available, and if JetBlue has a latest check-in time of 90 minutes (I am not sure; check that on their website), you may get in serious trouble. One thing you might do, if you can see that your flight leaves kind of in time in Warsaw, is to do an internet check-in from there; but it can still be risky.

A suggestion is to contact LOT, and ask them what they do recommend as transfer time in JFK to a flight with no interlining agreement (you may even reveal the airline); also do the same with JetBlue, stating that you come in from Europe.

I don't know whether it exists, but if you could get a connection leaving Warsaw between 09:00 and 10:30, you would be better off (maybe see what the Star Alliance website can offer). A connection via FRA or MUC or ZRH (if you are with LOT/Star Alliance) would be possible; aiming to get on a 10 o'clock transatlantic flight.

For the flight back, things are also tight, but not as bad, because you won't spend much waiting time when arriving in JFK. Again, you might check in for the transatlantic flight when you leave (this time in Las Vegas). But again, get some confirmation from the airlines, and also ask what you would have to do when you miss the connection. 22:55 is one of the last flight of the transatlantic bundle, and when you miss it, you will be stuck in New York for a day. So, it might be worthwhile looking for earlier connections leaving Las Vegas, or even aim for an overnight flight.