You have a solid security configuration! How are Avast and the Comodo Firewall playing together... any problems while running them?
You can add to your browser this two addons :
VTzilla (Free) -
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VTzilla is a Mozilla Firefox browser plugin that simplifies the process of scanning Internet resources with VirusTotal. It allows you to download files directly with VirusTotal's web application prior to storing them in your PC. Moreover, it will not only scan files, but also URLs.
The scanning options are embedded in Firefox's context menu and download dialog, making the analysis process as easy as clicking a single button.
LastPass (Free) -
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LastPass is an online password manager and form filler that makes web browsing easier and more secure.