First mailing list subscriber but scared and demotivated

you got a 3.33% response rate on people joining a mailing list to follow something that doesn't exist yet. People have crap attention spans, you want them to be both jazzed and to wait. That 1 person is your bullseye, your early adopter - you could multiply that 3.33% by probably 3-5 x if there was a product to show. Who knows if you targeted the real perfect users, it's a small sample set. The only feedback you got was a sign-up yes/or no - maybe you need to have the video beg for feedback in the comment section and don't sweat the sign-ups if it was on Youtube. on Instagram you could ask for feedback as well maybe (I'm not really an instagram wiz)?

My question is what have you done to establish market fit before you go too deep? If you did something and aren't kidding yourself, if you know the problem and the audience and they talk about the problem or lack of your widget then I wouldn't worry too much about it. I would ask the followers if they saw it and what they thought even though they didn't sign up for the newsletter.

you wrote: "I have months of work left to do even just to beta launch, in addition to my day job, and not sure if I should persevere. I don't know if people will pay for my service."

Rephrased it could read "I only have months of work left to get to my beta and luckily I still have a day job, I don't know how the market will respond to my service yet my email sign-up rate is 1 out of 30 for following my pre-launch updates"

Only you know if the product is really what the market needs based on whatever you did to determine it, nobody can tell you to keep going or not but yourself. Just realize that the success of the first video you made in converting viewers into email list subscribers is not the same as the future adoption rate of your service.