Usually babies cry when they need something, eg, sleepy, hungry, sick, want to change nappy or want attention. I put my baby on a routine so that I can somewhat "predict" what he is crying about.
As for bath, I try to bathe him at the same time everyday so that he can expect it and look forward to it. Babies thrive on routines. Make bath time enjoyable. I know it's tough to try to bathe him at somewhat the same time for you. Try to catch the time he is usually most awake to bathe him.
For growth spurt, he can cry up to every hr. That's what I experienced. Are you breastfeeding? If you are, you should latch him during the spurts so that your milk supply will increase. After your milk supply increases, he will slowly move back to his normal routine of feeding every 3 hours because by then your body would already have produced much more milk after the spurt phase.
If you are bottle feeding, during the spurt, you should increase his feed amounts and find the amount that is enough to satisfy him to last for 3 hours. Spurts are phases where baby's appetite increases very suddenly. It happens at around 3 weeks, 6 weeks, 3 mths, 6 mths and 9 mths. After the 3rd month spurt the rest are not as tiring.