Please don't ever consider giving a baby any of the nsaids like ibuprofen.
When my little ones were teething, the best teether was a very cold peeled hard and large carrot. Peeled to allow the sweet flavor to come through, large enough that the little teeth can't bite the end off, cold because that feels good. The carrot has a little give so it isn't too hard.
There are homeopathic teething remedies that often work well.
You don't say if you are still nursing him or not, but if he is not nursing 100% by now, you may want to be sure that there is absolutely no refined sugar in his diet. Fresh fruit is ok, but nothing sweetened with any kind of sugar or honey. Sugar can creat some of the symptoms you mention.
I have been working with nutrition for the past 41 years. Please feel free to contact me if you think I can be of help.
Blessings,
S.