Can I continue monetizing my game with the Personal version even if I have to upgrade my license because of incomes of over 100,000 a year?

That's something that isn't directly covered by the terms-of-service. I would say that you don't have to update Unity if and only if you don't use Unity anymore. As soon as you, as individual, earn more than 100000 a year you are not allowed to use Unity personal. So as long as you don't have to update anything on the game that requires the Unity editor i "thing" you should be fine.

Note that the terms-of-service has been changed and they differentiate now between "Commercial Entities" and individual persons. Commercial entities have to account for their whole annual turnover while for individuals only the money you actually earned from your Unity product counts.

Though as mentioned above that's just how i see it. I'm not a lawyer so if in doubt contact Unity directly.