Newly Diagnosed with TMJ -- advice?

My story is a very bizarre one, but I think I could be on the road to figuring it out.

It all started 2 months ago when one of my lower left teeth started bothering me; upon x-rays, it was found that nothing was really wrong with the tooth. The pain started 'moving' around a bit all over my mouth and within a few days, I acquired what I thought to be a terrible sinus infection. Left side of my face became very congested -- behind my eye, near the ear, post-nasal drip, etc. Doc put me on 2 rounds of antibiotics and steroids. Nothing helped. I was sent to an ENT who did a CT scan of my sinuses and found my sinuses to not be infected.

I do know I also grind my teeth because I woke up with my entire jaw contorted. In addition to the sinus problems,
I've been having muscle pain in the lower back of my head and neck which can radiate down to my arm. The dentist gave me 2 options for a nightguard, a softer custom-made athletic mouthguard which cost 90 bucks or a hard acrylic one for 350. I went with the cheaper one first. It seemed to make the symptoms much worse. Dentist suggested I go see an oral surgeon for TMJ consultation. He said to not use the softer nightguard as it makes things worse and to go back , get an acrylic nightguard, take motrin morning noon and night for a month, and go on a soft food diet. I also got put on a muscle relaxer which has helped me fall asleep. Wait a month and follow-up with him.

I had planned on doing that until that tooth started bothering me much more again. There was an amalgam filling in it so the dentist just removed it (and found just a bit of undectable decay underneath). That was yesterday. Pain is still there but seems a bit better.

In short, I've been suffering from horrible sinus pains, tenderness in the TMJ joints, dental pain and muscle pain non stop for 2 months. I'm becoming depressed. I would go and get the custom nightguard but I'm afraid I may need a root canal and crown in that tooth if the pain doesn't subside and I don't want to get fitted for a mouthguard that will become useless in a few weeks.

My question is... how has your success been with getting a custom-made acrylic nightguard?? Should I try and wait it out a bit to see if I need the root canal and crown (though no decay seemed to be near the nerve and there is no abcess) more or should I bite the bullet and get the nightguard asap to see if it helps my symptoms? Thoughts? Can my horrible sinus issues that are not curable to antibiotics be caused by my nighttime grinding and clenching? Does the mouthguard really help in allievating jaw muscle pain??