You had mentioned before that every few minutes it would freeze on wifi.
if it stayed solid for 30 minutes or more on ethernet, I think we can eliminate the browser as the issue.
This is either the wireless router, or its the wireless card on the mac.. I hate to do it to you but we need to isolate a bit further.
Easiest way to do that, would be to go into the router. Remove the wireless password. ( only temporarily, just for the test)
Once the password ***** ***** your mac should be able to connect to the open network without any password. ( So will anyone elses phone or computer within range, so lets only test this for about half an hour)
The big question is, with the wireless password ***** off, does your computer still stop and freeze every few minutes.
Let me know when you have had time to test this out, or if you have any questions about the process.