While sadly I can’t shed much more light (well, not as much as I’d like anyways), I’ll try to clarify what I can.
With reference to what you quoted me on:
You mentioned using Firefox, which is good. As is Chrome. Though I’m sure I can guess why you didn’t go with the latter.
lol
Basically, I was just trying to say that as long as you keep whatever browser(s) you prefer up to date, the more you minimize the chances of becoming infected while surfing. [Side note: Once I had the misfortune of NOT maintaining my normal habit of downloading all the apps/updates/drivers/etc BEFORE I reinstalled the OS (whether you save them to flash drive, another hard disk, or burn them to cd/dvd/etc) and went to Google for a driver it needed, and the very first link I clicked infected the unit. /facepalm] At any rate, most infiltration occurs in browsers due to scripts, flash and Java (I use neither), or old exploits that have long since been patched for in the current version of the browser.
Kaspersky has a solid reputation for some years now, but the last time I tried it was more than 8-10 years ago, so I can’t really comment on anything there, other than to say that I have a good impression of it from what I’ve read previously on security forums. The fact that it includes a firewall is a plus, and puts you further ahead of the game than others who don’t use one.
The fact that you don’t, IMO leads me to believe that you have no need to upgrade then. As long as the hardware is fulfilling your needs (not getting bogged down by demands on it; IE: converting video, needing low-latency/high speed for tracking high-res multitrack audio, or high-demand gaming [you old ‘rail-master’ you LMAO… Q3 reference I don’t expect you to get of course ;)] you really don’t have cause to upgrade.
The ONLY exception I could see is perhaps for video chatting with the grand-kids/family/etc for a Webcam that would feed 1080p, and it’s associated app (Google Duo, Skype, etc). But, even then, most basic hardware that was out during the life of w7 should accommodate that handily (especially given you’ve already upgraded the amount of RAM). So again, not really a requirement unless it’s like first generation hardware that barely made the cut during the transition period from XP to w7 (unlikely).
Of course they do. 
More current cpus have hardware ID codes, and more stringent reign over how files are handled (at the hardware level) than what they did before.
The more they control what… Never mind. You already know.
I’m not sure I’d go quite that far. But, I haven’t looked at retail (prefab) in years. I’ve always bought my own hardware and assembled exactly what I needed, based on the intended use of the machine. (Gaming rig, Audio rig, old repurposed POS for surfing, etc)
Haven’t seen that, but I’m already skeptical. What’s the motivation (from their POV)? If not to sell hardware, then…?
In your case:
- You’re not doing 30 things at once, so no need for an 8-core, multi-threaded, 12mb L2 cache, etc behemoth. (whatever dual or quad core you already have is more than ample to do what you’re asking of it.)
- no massive data handling, so you don’t need 8gb or more of Ram.
- no major data transferring, so you don’t need 4tb plus of HDD.
I just can’t see the need for you.
Similar to my mom, there’s no reason to upgrade.
Hell, the only reason she’s been upgraded to where she’s at, is because I wanted to put a terabyte sata drive in her machine, and her mobo didn’t have sata.
Which, by default meant she needed a new cpu, and psu. Even with that, she spent less than $150, because I had all kinds of spare parts laying around. Memory, cpu, psu etc.
Barring a hardware failure, you shouldn’t need to worry about any of that. 
Sadly, I can’t answer here, unless you are comfortable with command line use of Linux.
I’ve read that there are some that are almost “windows-easy” to install and get running. But I’m not familiar with them firsthand. Hopefully another member here could offer suggestions.
Absolutely not.
Stick with what you have, but consider looking further into the Linux variants! Definitely covers the latter comment: “I don’t want or need stuff I’ll never use.”
Especially when you talk about buying HP and Dell (the only two general mass manufacturers of prefab that I’d ever recommend). Bloatware central, but usually very solid hardware from first tier vendors.