Talking to 2-3 of your target customers will help you understand how you need to change the idea. And keep doing it until you get consistency in their feedback.
You also get bonus points if they are willing to pay for the privilege of getting access to it first while you work with your first small set of users.
M == minimal
1. Do you think anyone would use my MVP or service?
Depends on whether you build it or not. If you don't build it, the probability of its success is zero. If you do build it, the probability of its success is nonzero.
2. Have I missed any other market segments?
Yup. All of them! You miss 100% of the shots you don't try.