I have a similar style of business, ~10K customers, ~150k users, ~7yrs.

The key points are:

- offer email support, but don't offer phone, video calls or remote support. This works for most people and forces them to properly phrase questions instead of just "jumping on a call" (so you can then effectively train them over the phone, which doesn't scale).

- offer as much self-service as possible

- work at your own pace and it's ok to just not work some days.

- finding a niche is hard, but they can be surprisingly basic. You're just saving someone time, effort, worry etc.

- lean on global cloud services for reliability. Let them do that.