Doesn't matter about their current velocities. The universe is 14B years old. It's bigger than 28B light years wide. Therefore the universe had to expand faster than the speed of light.

Further, light goes through the universe. The universe expands outside of itself into who knows what. We have no idea if the speed of light applies outside of the universe. Same for thermodynamics.

That answer seems kinda counterintuititive to me considering that the universe is larger than the equivalent size it should be for its age and the speed of light. Thus, the expansion of the universe has obviously gone faster than light and has broken a major physical limitation of the universe itself. Why would we expect that expansion follow other in universe laws?

The last sentence you wrote is essentially correct. The b cell that gets activated first, regardless of affinity, is the one that gets clonally replicated. Those clones have some randomization of their antigen matching site -> the ones that bind better get selected for future cloning -> ad infinitum until infection is clear.

Also, there are memory b cells of previous infections. Infections tend to be geographic; standard respiratory infections, hand infections, foot infections, etc. So those cells are already there for clonal proliferation.