For jendon to pass a target lock, can he still do so even if no ships are within attack range? Is there still a combat round?

Use the shuttle title. Target lock first round, then pass the lock off?

"During each game round, players perform the following four phases in order:" -Main Rulebook, page 5.

So yes, each game round has a Combat Phase, even if nobody is in range.

Yes. The Combat phase is still a phase that gets put through the sequence, even if no ships can use it for combat.

Jendon passes off his blue TL token at the beginning of the Combat phase, before anything else happens during the combat phase. No combat is required to pass it off, only to have the ships survive to the start of the phase.

In a casual game, most folks wouldn't bother with the Combat Phase if the ships were clearly too far apart, unless you've got the ST-321 title in play, like you did. Then it's follow the sequence strictly. Darned handy that card.

Don't forget things that trigger in the End Phase either. I had a game over the weekend and my opponent was always keen to get into the next turn straight after the shooting was done and I kept forgetting to use my R5 Astromech to sort out my damage cards. I had one hang in there for 3 turns. Doh!

Since you are not allowed to measure range outside the combat pahse (excluding targetlock actions and other range depending abilities/actions), it would be rather hard to determine if there should be an attack phase if it was only there if attacks could happen