hello..read thru ur query...accordingly i must say that ur lucky that crack in the tooth has been detected...many situations cracks cannot be detected and patient feels pain no matter what all treatments v do...rootcanaltreatment is required(i strongly feel)in this case....and crown also required otherwise the tooth after rootcanal treatment may fracture...also the success of the RCT depends on the place where the fracture has occured...so i strongly give opinion that rootcanal treatment is required for crack...pain that ur feeling after antibiotics is due to exposure of pulp thru the crack...so go ahead with the treatment...if its a vertical fracture extractiin has to be done....as it has poor prognosis...so follow ur dentist go ahead with the treatment..hope ur benefitted something from this reply..have a healthy day!!!

Thanks for your query, I have gone through your query.
The cracked tooth can be treated with normal tooth color restoration if it is involving only enamel and dentin. If it is involving the pulp then it has to be restored with RCT or extraction. If the crack is extending into the root then the tooth cannot be saved, it has to be extracted.
To know whether the tooth is infected or not, you can get a radiograph done, which shows the presence of infection or extension of the crack. Consult a oral physician and get a radiograph done and later we can decide the treatment.
I hope my answer will help you, take care.