That's why they call it a "paradox"!
but it's not even a paradox, baal will always go back in time yes and he will always meet that Mitchell from the original timeline, there no paradox occuring because there are two seperate timelines at play.
No disrespect,but you are incorrect.
First,there is no alternate timeline.Since Baal's initial trip to 1933 caused people and buildings to dissapear in real-time,there was only one timeline at any point.
Second,what has happened with Mitchell is a 'logical' paradox.Instead of going back in time and doing something that would stop you from going back in time (like killing your grandpa) ,your trip to the past causes your future self to initiate the trip to the past.
In example form,let's say you rear end a car on Main Street coming home from work.
You then go back in time to prevent the accident.
Since you can't call yourself and expect your present self to believe the truth,you(future self) go to Main Street and close the road,hoping you'll take a detour and avoid the accident.
A driver in front of your present self panic-stops at the closed road,causing your current self to rear-end the car.
The above sequence makes perfect sense(considering I made it off the top of my head lol).It's a paradox because your time travel into the past created the present that inspired you to change the future-by traveling into the past.
This is what has taken place with Mitchell.He is saved from the timeline changes by the Tok'ra Stargate,ends up at alternate Earth,lives on Alt.E ,then goes back to 1929 via Praxion Stargate,waits until 1933 to kill Baal,then lives his life alongside his grandfather.
So that future Baal can try it all again,fubar the timeline,and start the cycle again.
After all that typing I HOPE you understand lol.