Help with several questions: Experience with Giardia in cats, medication + infection in humans, emergency practice?

After my mother's best friend told us at home two weeks ago that her cat had Giardia, my tomcat has now also been infected (I have two tomcats). He's been suffering from diarrhea since December 31st. At first I thought it was due to the fireworks, but then yesterday I got the diagnosis after a stool sample. Giardia, and the vet said it was a pretty serious .170.

The helpers wanted to administer the tablet to my cat together, but he resisted, biting his tongue and foaming at the mouth. Both cats are now receiving Metrotab (metronidazole). They take it for a few days, then take a break, then take it again, take it for another few days, take it again, and then take another stool sample…

The two refuse, run away, and hide. I've tried everything. I've put them in treats, stirred them in and under licking paste, and finally crushed the tablets, mixed them with water, and administered it in a disposable syringe. My mother helps me. The cats have to lie on their backs, otherwise it all spills out anyway. It's so difficult that I've had to waste several tablets. It stresses me out. The first and second time, it took an hour to give them to both tomcats; this morning, it took "only" 37 minutes. My dear mother helps me; without it, it wouldn't be possible. The good thing is that my cats don't scratch or bite, but they close their mouths and move frantically. Really difficult…

Since my cat has had diarrhea, I have no appetite, I feel sick and for the last 2 days I have also had diarrhea, so I go to the toilet and think I HAVE TO GO RIGHT NOW but nothing comes out… Last night I felt so sick that I almost had to vomit and I had extreme chills (maybe fever, thermometer is broken) and stomach pains

My first question: Have your animals ever had Giardia? Is it normal for them to drool so much? I haven't seen it happen with medication before (after 9 years with them).

2nd question: I think I might have been infected. It's Saturday… do you know if the German Red Cross (DRK) general medical on-call service can test for Giardia? Definitely not, right? Should I go to the hospital? Or just wait until Monday? I'm feeling really bad.

3. Question: Do you have any general experience with this?

best regards

Tooth Fairy