That’s a lot of questions…

We do have a pretty good understanding of physics, using the standard model we could predict the Higgs Boson, and the muon’s abnormal magnetic moment with an incredible precision. While cosmology isn’t as precise yet, we’re now in the precision cosmology era so new forces don’t come out of the hat.

A few new force I may think off

• Modifed gravity is an alternative theory to dark-matter which would require gravity to behave differently with low acceleration, . While, there is good reasons to think it’s not working, it’s not yet strictly excluded, so a new force can come from here

• Inflaton, would be the force associated to the so-called dark-energy which explain the universe expansion. However, the property of the inflaton particle still have to be understood, but that would be a new force

• Higgs field being a boson, it’s a force

• Supersymmetry is a pretty popular extension to the standard model (as it would solve a lot of problems, and provides theoretical candidate for dark-matter) and it involved a new batch of boson --> New force