Ok, one question at a time.

No, metformin does not translate into insulin - no really good stats out there but about 40% of Type 2's will end up on insulin. There is a whole raft load of relatively new meds to work through between metformin (a first tier treatment) and Insulin (a Tier 4) treatment.

The best way to ensure you stay off insulin is make "lifestyle changes" - find a diet that "works for you" and that you can follow "forever" that helps control your blood sugar levels.

That doesn't guarantee "no insulin ever" but it is the most "YOU can do yourself" to lower the odds.

Second, if you need to "lose some weight". If your BMI is over 25 that makes you far more resistant to using the insulin you produce yourself. So if you want to remain off insulin then you need to make your own "work better" and losing weight is the "only" way to accomplish that.

Is following a (new) diet and losing weight HARD - it sure is. But the alternative is more and more meds and then insulin - you just have to decide for yourself how much you are willing to do to avoid the increased/escalating Tiers of medication.

A glucose meter is "valuable" at any stage of diabetes. I take NO Meds and still use a meter daily. That helps me to stay off meds. I get immediate feedback of something that I shouldn't have done or shouldn't have eaten - kinda like burning your hand on a hot stove - you don't do that too many times before you learn - but it is not mandatory.

Kinda already answered your last question - No, the "majority" of Type 2 diabetics never ever use insulin, some never use medications "at all".