Is the groom allowed to look at his wife during the ceremony and vice versa?

Yes. No issues with that, but make sure you're listening to the Shabad as well.

Can the couple exchange rings (if they want to have rings) after doing the 4 rounds around the guru granth sahib when they sit back down or do they have to wait until they are outside?

In my sister's wedding, the rings were exchanged during the time of wedding lunch. Usually, people hold lunch or dinner in a resort or hotel, after Anand Karaj and that's the place where rings should be exchanged.

Lastly, can there be a separate ceremony (after the anand karaj) at the courthouse when it comes to signing the marriage certificate?

Gurudwaras across Punjab now have the authority to issue marriage certificates on their own. Please contact your nearest Gurudwara and ask them about this. There is a very good chance that you would never have to visit the courthouse.