I am having Windows 7 not only at home, but at work also and successfully doing web apps and sites.
My suggestion is, install Microsoft Security Essentials (you can get a copy of the installer out of archive.org) and definition files are still published for it and are up-to-date. MSE is what became Defender in 10. The Defender in 7 is not the same and doesn't scan for the same things. MSE is needed to replace it.
[1] https://support.mozilla.org/en-US/kb/firefox-users-windows-7... [2] https://support.google.com/chrome/a/answer/7100626
W7 is just fine. Daily driver on multiple machines, never been "taken over" or turned into a crypto miner or a hub for a bot network, never had a single virus or other issues.