Concerned I've been hacked. Should I use 3rd party anti-virus. ?

Do not install Intego or any other AntiVirus. You will regret that decision and find it is very difficult to remove once you start experiencing problems. Feel free to use the Search option on the top of this page and enter "Intego" for more information.

For the issue with your clock, are you using a VPN?

The best way to tell if you have any Malware installed on your computer that is running in the background is to post the free EtreCheck report using the Additional Text option when posting. This report contains no personal information and will show what processes are running on startup that may be interfering with Mac OS.

How to use the Add Text Feature When Post… - Apple Community

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect or speed up your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Your exceptionally well-crafted Macintosh computer does not accumulate filth that needs any third-party anything to clean it. Everything needed to run it efficiently was included in the box, except ONE: a drive on which to store a second copy of your files in case the first copy is damaged or deleted by accident. The backup software, Time Machine, is already present -- integrated deeply into MacOS.

See this user tip:

Effective defenses against malware and ot… - Apple Community