With something that severe, I would recommend going to the oral surgeon and getting a different antibiotic if there's no improvement. I would also recommend that the tooth be removed as soon as possible. If they can't open the mouth enough, they should try to at least clean the area or try to drain any pus in that area to relieve that pressure.
When I went to the dental clinic a few weeks back because of pain, i asked what would work because over the past 4 years, ive been in constant chronic pain.
The DMD told me that typically, after a while, your mouth builds a tolerance to the pain as any other part of the body would. She suggested taking a dose of ibuprofen and then when it was time to take another ibuprofen, take an acetaminophen pain killer instead and continue to alternate.
Apparently, after the 8 hours (if it's 800mg prescription strength ibuprofen), the ibuprofen is still working a bit and the acetaminophen will take over and help whatever part of the pain the ibuprofen didnt.
I've recently started trying this after visiting the hospital due to oral pain again yesterday with Prescription strength ibuprofen and percocet and it seems to work rather well (for me, hardly anything ever works when it comes to pain killers) so try this and see if it works.
You'll probably want to take the weaker medication first. I'm not sure if this actually works, but my theory on the topic is that although the weaker one may not work too well to begin with, it's still working to get some of it. Once the pain's "resistance" to the medication starts to get broken down a bit, the stronger medication shouldnt have to "break through" that barrier too.