Should I terminate Aviva Group Term Life ($280k) & Personal Accident ($100k) or should I increase the coverage? As I am going to MR 3yrs time will this plan still cover what I did outside NS?

It covers until you're 70.

It's the cheapest term plan available. So I'd recommend to get more if you need the coverage.

However you should still get coverage for Critical Illness from a private plan instead of group due to limits and limited conditions covered.