Don't worry too much about the science of this. If you can manage that, this was a lovely series with a good ending.
Spoilers/problems:
Ok, it is not easy to avoid the problems in the "science" of this.
For example, how did this loop start, since he is the father of his own father (or grand father, can't remember).
Since this is the case, this loop could never start, since that particular child was never originaly born.
Please explain exactly why this particle times splits you into 4 timelines.
Since it also splits you into the future, then all participants will also pop up in the future of this story regardless of what you have done in the past.
This will not just stop.
But, the storyline was stopped by the explosion not happening... But the child does exist. Meaning, the original time jump by Elias still happened.
The most annoying thing about this is that they have used a kid that does some good crying scenes, but he needs contact lenses to have eye colour approaching his own self in the future.
Surely, England with a population of around 70 million could find someone with natural eye colouring that is correct or close.
-'Cause I am firmly sick of stupid contacts like this after several decades with Johnny Depp running stupid with different contacts and makeup.