What checks should I go through if my laptop can't connect to the internet through tethering?
Having a limited connection is a common issue in Windows 7/8/10. The only good method I've seen that works is doing a system restore to a earlier restore point (not a full wipe of the laptop). It'll be under Backup and Restore in Control Panel. Every time Windows updates it creates a backup which you'll want to use to undo any issues that may have caused the limited WiFi bug.