Computer Help and Support

To check the Ethernet, open a command prompt and use the ping command:
"ping -t router_ip_address > results.txt"

The -t switch lets it run until stopped by a ctrl-c.
The > results.txt pipes the output to a text file named results in the current directory.

https://support.reolink.com/hc/en-us/articles/360012076133-How-to-Use-Ping-Command-on-Windows-PC

When you check the results file, time outs indicate the link from your pc to the router isn't good.
It may be the cable or maybe a failing port on the switch.

Cat6 should be rigged with strain relief at points where it enters or exits a wall. Having subject to weather and wind and possible animal nibbling are concerns.

I don't like running regular Cat6 cable outdoors. You may want to consider sleaving the cable or setting up a better WiFi option. You can put a repeater in the house nearest your office in the garage and get an amplified adapter for your office pc like this:
https://www.newegg.com/wavlink-690a5d-usb3-0/p/0XM-00B5-00048?Item=9SIA6PFBHF2607&utm_medium=Email&utm_source=ShellShocker&cm_mmc=EMC-SD022021-_-SD02112021-_-Item-_-9SIA6PFBHF2607&tp=i-1NHD-Q7H-1Hk-4pLgG4-2G-BLPd-1c-DO0-4m577C-l5gzXU5hT5-25FlqP&om_rid=4423291796&om_mid=4944&email64=cmtpYzFhdGlzc0B5YWhvby5jb20%3d

I'm not sure about your other 2 issues.