Sanctification of believers, spiritual health and spiritual nourishment.
Salvation comes at Baptism. The purpose of the Mass is for spiritual nourishment, sanctification, and the maintain spiritual health.
Thus, by not attending Mass--your salvation is not affected since it does not undo your baptism. You still have a relationship with Jesus.
However, attendance at Mass on Sundays and Holidays is necessary. Intentionally missing Mass on these days is a Mortal Sin.
The Mass is the renewal of the covenant. Asking "How is one's salvation affected by not going to Mass" is like asking "If a husband and wife never kiss, or otherwise have any physical signs of love for each other, how is their relationship affected?" Does that undo the marriage? No. But a marriage without physical signs of love--well, you have to ask yourself how healthy the relationship is.
A Catholic who never wants to go to Mass--you have to ask yourself--how healthy and strong is their relationship with Jesus if they never want to go to Mass?
You mean like on Good Friday--when no Mass is celebrated anywhere in the world? You mean like that?
Depends on what you mean "affected." See above.
Again, the purpose of the Mass is for spiritual nourishment and spiritual health.