Question about Nraas Traveler

Also, I remember one time I plum the mod there was something with the pregnancies. My qouestion is - If my sim traveles while his wife is pregnant - but she does not come along, When he returns - will it be to the middle of her pregnancy / after she gave birth / something else?

When a sim travels, everyone left in the homeworld is put in suspended animation until the traveling sim returns. It works just like visiting WA, Uni, and ITF worlds. So in your example when the sim returns home his wife's pregnancy will be at the same state as when he left.

Traveler does have a setting to allow pregnant sims to travel, but that doesn't affect pregnant sims left at home. The only 'pregnant' sims I've had travel are sims who got pregnant at University where sims don't age. Those pregnancies don't progress at all while at University, they start progressing once the pregnant sim returns home.

I want one of my sims to "visit" in some other worlds, but once he returns to the homeworld, I don't want the worlds to stay connected. (I do want to continue with the same save).

When your sim travels to an installed homeworld via Traveler, a new instance of that world is created in that save folder. Upon returning home that world file remains in the save folder. You can delete it if you want but it doesn't do any harm to leave it there. Only one world is ever loaded up by the game.

Traveler does not allow sims to travel to other ongoing saves. You can, however, copy the .nhd file of another save into the save folder of your current save and have your sims visit. But that's a copy of the other world, and so would progress independently than the original.

What will happen if i will uninstall the mod after he returns?

The worlds he visited would remain in your save folder (unless you delete them manually) but he wouldn't be able to visit them again.