No. No, they're not.
There could be any number of reasons why someone is subscribed to your comic but not actively engaging with it - maybe they've subscribed so they can find it again and read it later, because they don't have time right now. Maybe they're the kind of person who wants to read a whole bunch of updates at once, so they're waiting for a pile of new episodes to build up before they read it. Maybe they're really, really shy and don't like commenting, but are still enjoying your comic.
No. If it's just a couple of hours, it's entirely possible that your readers are just in a different timezone than yourself, and just aren't awake to see your post. Also, not all subscribers get notifications for wallposts, I don't think - at least before the launch of the new app, it used to be that app-users didn't get those notifications. If the majority of your 100 readers are app-users, that might be a reason for the silence too!
Also, I've put years into posting art online to the sound of crickets chirping, because I prioritize drawing my own original stuff, and the internet prefers fanart. I'm used to feeling like I'm shouting into the void - it's not anyone's fault that people didn't respond. Original content has a harder time getting traction online, and it always will.
No, but it sounds like the issue here isn't with your number of subscribers or their silence, but rather with your self-confidence. When someone compliments you, believe them. It's 99% likely that they are sincere - and if they're that 1% who are, what, lying to you because they love fake-complimenting people or something? Then take that compliment and run with it. Someone said something nice to you - awesome! It doesn't matter if they didn't mean it.
Also, re: how many subscribers you have vs. how many of them actually read your comic/comment. I have 3600+ subscribers - I still have only 30-50 people who comment regularly on the pages. That is a LOT of silent readers, and probably a whole bunch who don't read it but are still subscribed. That's normal. You're always going to have a big bunch of your audience who are passive.