Sleep training books

Do any mommas have any good books or groups you belong to for sleep training a toddler? My 3 year old refuses to sleep without being rocked to sleep or having butt pats. He has an appointment with a pediatric sleep doctor May 1st but I’d like some tips before then. He was doing great for a few weeks until he because afraid of everything. He does sleep with a night light as the reflections scare him. He listens to lullabies all night long otherwise he wakes up to the slightest sound. Normally he is up for 1-2 hours in the middle of the night but some nights we get lucky and it’s for maybe 20 minutes. Sometimes he goes down easy for sleep but then other nights it’s a fight. He will cry for hours on end until about midnight and then is up by 6 am. We have another baby due in June and I can’t keep doing this. I will also not do cry it out because he will cry for over 3 hours straight with no end to it as well.