Exposure to a virus doesn't ensure infection - there is some probability involved, depending at least partially on the number of virus particles that you are exposed to, over what period of time.

Viral load is literally a numerical expression of the quantity of virus in a given volume. It is often expressed as viral particles, or infectious particles per mL depending on the type of assay. And a higher viral load often correlates with the severity of an active viral infection.

If you’re infected by a couple of individual viruses, it’ll take a while before it starts spreading throughout your body, which will have more time to prove an immune response. Compared to essentially bathing yourself in it for days at a time.

afaik viral infections increase at an exponential rate. If the initial load is higher, the peak infection before your immune system can get things under control will be much higher/dangerous.

Ex: 3^10 v.s. 30^10

No, your symptoms are affected by the number of viruses in your system. The virus is constantly replicating and your immune system is constantly destroying them. If the rate of increase is greater than the rate of decrease, you will not recover.

Agree but they may also be constantly reinfected.