The only thing you have mentioned that might be precluding you from making good connections to web sites like banks is something you seem to feel is "protecting" you in some fashion -- that is your Third-party anti-virus. The only thing worse would be also running a VPN you added yourself "for improved security".
Nothing could be father from the truth. This sort of software breaks into your previously-secure communications, so that it can be FIRST to scan incoming data (which is not a threat on your already well-protected Macintosh system) for imaginary threats such as antique Windows Virus look-alike strings.
I recommend you remove all such snake-oil using the manufacture's un-installers, and never re-install them.
this article may give you a better idea of what's really happening:
Effective defenses against malware and ot… - Apple Community
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