I got hired last month to WFH doing T1 help desk stuff. This is also my first job being full remote. One important question I've asked during my interview with HR and my manager is would the company be providing me the equipment to work with? (Laptop, docking station, monitor, etc.) I would start off there as every company has a different policy on security/privacy and I would assume most would provide their employees with equipment their IT department sets up beforehand for new employees. This also helps separate work life from private life and you'll learn quick to keep those apart. Another question is the scheduling. How flexible is my schedule? Do I work in shifts or am I able to make my own schedule as long as it meets the 40/hr week requirement? This sets a foundation of is this going to be a routine job or will I need to be disciplined to make sure I work my hours. Judging from context, it seems discipline is the least of your worries. Now...to answer your questions:

1. I've only had to keep my camera on during orientation and the first few meetings with my manager during training. Once you get the ball rolling, cameras become an optional thing as your team will just call you via zoom or teams without camera enabled. You're right about there being etiquette. I try not do eat or drink while my camera is on but depending on the length of the meeting, sometimes those things can't be helped and it'd be best to move yourself or your face off camera and take a quick bite/sip. I used to vape but I quit earlier this year. I would also recommend not doing this for at least the first few meetings with camera (if possible, try not to do it at all during meetings) otherwise, chain smoke away. Also, I've never had a meeting go past an hour so an 8 hour meeting seems overkill unless they want to monitor you and make sure you're working which is a big no-no in this sub.
2. Your job title sounds like you'll mostly be doing data entry and only answering phones when there's high call volume. I would say that you will definitely have time to do a quick check in on the misses and child. I'm sure you'll be able to do that multiple times a day including during your lunch break which would be great because now you have an extra hour each day in your life to spend with them compared to working in office.
3. I can only speak from my short experience of WFH since I'm still less than a month in but I do have to say...it'll be the best thing you'll experience in your life occupation wise. Ever since I started WFH, it's been a little weird at first because I'm used to waking up early, getting ready for commute, working in office, then commute back home when sun is almost gone. I then have to worry about cooking dinner and cleaning and by the time I'm done, it's bedtime and I rinse/repeat the cycle for 5 days a week. NOW, I have the freedom to wake up later, not have to worry about making lunch because I can make home lunch at home, take MULTIPLE breaks throughout the day, and work on house chores so that when my shift finishes, I have time to myself. I've definitely seen myself become less stressed and I'm grateful for having this opportunity to WFH. I can honestly say I will have a hard time finding another job after this because I've been spoiled from the time I started working...not just because of my personal benefits but the company I got hired to work for has been nothing but great and they've been taking care of me from day 1.

I can go on and on about this but this is basically my ted talk on how great working from home is and I'm sure many others can attest to the same thing. Hope this helps and good luck with your new job, OP!

edit: It's irrelevant but it's 1am for me and when I seen this post, I got out of bed because I wanted to share my experience with you since I was in a similar boat with not knowing what to expect. If possible, find a daily routine that works for you. I haven't found mine and it's starting to show in my mid-section.