Yes, Optimal was the correct term.
1. Are these recent after the new install? Although these are really insignificant to most issues. You can try the following and see if it helps get rid of them.
open a admin CMD prompt.. type or copy/paste each of the commands to reset it.
net stop winmgmt /y
winmgmt /resetRepository
winmgmt /verifyrepository
net start winmgmt
2. I would agree at this point without being able to do more advanced testing. Wifi adapters are pretty reasonable and may be worth buying.
3. Yes, I agree. Mine never seems to be consistent. Below are few more suggestions you might try that may help with at least some of the connection issues.
I downloaded your manual and it looks like your router offers WPA2 AES mode. from manual "WPA2 gives you two encryption methods, TKIP and AES". I recommend changing it to WPA2 AES for best performance.
What is the IP of your Router and starting IP of DHCP server? I recommend setting similar as shown below
Router - 192.168.1.1
DHCP - 192.168.1.100 - 192.168.125.
Now assign your computer static IP's such as 192.168.1.10, 11, 12, 13
After setting static ips on all computers then add the IP and computer name to your hosts file such as following example:
192.168.1.10 computer1
192.168.1.11 computer2
etc
You are welcome for the help!