How the heck are we supposed to find coverage?

I work at a fancy corporate site, corporate towers. You can't just show up as an SRO, you won't know anything! We only have so many officers on my team and I'm a key player meaning because of my high availability, I'm the go-to guy for filling in shifts.

This leaves me feeling stuck when it comes to calling off. There will be days I'd like to call off but even if it's before 4 hours, or even the night before, I'll be reluctant to call off therefore won't even do it. I just don't know what my boss will do if he can't find coverage, get a SRO / flex officer ? Then what? They'll show up and won't even know what to do, it's crazy. I don't even know... Am I making sense?

Moreover, I feel like it's stressful for my boss because of this. I've done a lot of heavy lifting when it comes to covering for people but he still harasses me and makes it seem like he's doing me the favor and that it's no big deal because he'll bring up how "I'm not busy," or not doing anything outside of work anyways because I'm single and live alone whereas he has a wife and kids. I'm a full time student, I just never told him that because he never asked, so I'm not going to just bring it up. What I do outside of work isn't his business, that's how I see it.

I even believe he put a tracker like an air tag or something on my car the day before my 3 days off because he knew where I was the morning I was to return to work... But that's a different story. Also, while on the topic, isn't it weird how the finger print dude during orientation randomly told me "don't hide anything from him, he will find out." For context, finger print dude asked me what my site was, I told him, and he knew the manager. Weird, right?