tongtong,
My boy is also having fever now, since Wed afternoon.
1) 37.5 to 38.5 - Paracetamol, >38.5 ibufen/nerofen. But for my boy, paracetamol works for all temperature.
2) Yes, come and go. usually peak at night/midnight time. For my boy this time round, fever at early morning, after lunch and night time, other time, no fever.
3) old people say cannot take bath. But scientifically no harm, just dry him immediately so that don't get cold. Same as wash hair.
I don't give med according to what suggested, only give when fever is high. Usually fever gone in about 30min after taking med, for my boy.
Hope your son recovers soon.