Many people already said reasonable things.
I especially agree with this notice:
You wrote before, that you had serious issues with depression.
Depression, depressive way of thinking is exactly what makes us interpret and perceive everything in the most painful way possible. To overthink, to concentrate only on painful emotions, on bad side of everything and draw attention away from anything good.
You concentrated on that friend's reaction, interpreted it in dark, painful way and then put too much value to it, estimating it as the most essential feedback among all you've got. In the same time, your attention was drawn away from positive reactions of those 10K subs, which you interpreted as something superficial and not important.
Depressive thinking is a cognitive bias, skewed way to perceive reality. It doesn't show how things truly are.
I suffer from this depressive bias a lot, too. I don't know how to completely get rid of it. I only can remind myself from time to time, that I have it and force myself to analyse everything from different angles, not only from the saddest one. It may be very hard and sometimes it requires time, but if I manage to do it, it helps.
I would suggest to re-analyse everything about your comics and about feedback from readers and from your friend from different sides, more objectively, when you'll calm down. This is what I would do (well, ideally).
Also, what about making Q&A section or fan-art contest? It could show you a bit more clear picture of how really involved are your readers into your work, give more clues, is their interest deep or not. It's a good chance to receive more feedback from more different people in any case. If you're insecure, it maybe scary, but it's a good experiment to sort things out. To be honest, I'm sure that you underestimate your reader's love.
Well, maybe I was somewhat drawn away from the main topic, but this is the thoughts which came to my mind when I read it.