Aggression in my English Springer Spaniel

Question
Hello, i wonder if you could help me. I have a 7 month old English Springer Spaniel who is incredibly lively and boisterous which I totally expected because of the breed and are qualities i love in him. What i didnt anticipate was him showing aggression towards me and my children. The problem only seems to occur at bedtime when i ask him to go up to his bed he growls, snarls and snaps at us in protest! This has only been happening for the last week but it concerns me greatly. I did lots of research on puppy training before i got the dog and have been following the guidelines on establishing yourself as the pack leader but they dont seem to be having any effect. We eat first and feed him after, he's not allowed on the furniture or upstairs to establish boundaries, we call the dog to us to give affection (most of the time!)and He's been crate trained since we had him at 9 weeks, he has also completed 10 weeks of training at a kennel club registered school which he passed (just about!) however his behaviour at the moment seems to be getting worse not better. He has always pulled on the lead in the park (but in training class always walked to heel perfectly) but just lately this has got really bad and he is really strong now, im so afraid he's going to hurt his neck. He used to respond to his name when walking on the lead and when off the lead but now he seems to have selective hearing! Im wondering where i have gone wrong! His lead walking is so bad now we have to let him off the lead in order to enjoy the walk otherwise you end up with swollen hands and fingers and a bad back from him pulling and jolting forward, however i feel that this is his aim and we are giving in to him which isnt teaching him respect. Also due to his energetic nature he needs to be off the lead in order to burn energy otherwise he would be very unsettled at home. I could really do with a bit of advice regarding my unruly puppy! We all love him so much and have really tried to do right by him but we seem to have created a monster (slight exaggeration because he is very cute and loveable most of the time!). Oh and leg humping is a problem too despite having been castrated at 5 months old! He is a very dominant dog who Im afraid will turn into a living nightmare if we dont do something now or are these things he will just grow out of? Any advice would be gratefully recieved.
PS when he does growl and snarl at us my response is to shout NO, grab his collar and make him go to bed. Is this correct or is there a better way of handling him? I do not believe in smacking or hitting dogs in any way shape or form but that is what everyone is telling me to do. Tap him on the nose, Im afraid this will make him aggressive or untrustworthy, am i right or is it neccessary in some dominant dogs, I really hope there is another way of dealing with his behaviour. Please help.
Thanks
Sarah

Answer
Hi Sarah, It sounds like you did your homework in the beginning, but did not stay with it. You are right that aggression begets aggression. There is no need to hit him. Let's address the walking on lead. Go back to the basics and get a properly fitted collar, or "Halti", and reschool him on leading. Make him heel, you will not hurt his neck, but he will hurt himself pulling if you let that continue. If you need to go back to obedience school for a refresher, it would be great.  But if you can do it at home, be sure to put the time into it every day. I like to break up my training sessions into 20-30 minutes of refresher in the morning and again in the evening. Being a high energy dog, have a long rope with you or let him run AFTER he has done his obedience work. If you live in a rural area, take him to a field which is fenced in and let him run, or take him for a jaunt in the woods. But he should walk nicely at a heel on the way there and on the way home.  
Now, bedtime needs to be corrected. He knows to crate up. How did he get from being well crate trained to thinking that the crate is a bad place? Think on it and write back if you need to.  I would put his training collar on him, walk him to his crate and tell him to go to bed like a good boy. When he goes into his crate tell him how good he is and give him a nice bone to chew on or a treat. There is nothing like a nice soup bone to chew on while in the crate. But let it be the only place he can chew his favorite bone. No crate, no bone. If he is becoming more and more dominant, roll him over, gently put your hands on his neck to hold him in position an stare him down. Let him up when he looks away. He will quickly remember that you are the Alpha dog. Don't make it a big struggle. You can do it when he is already laying down and just roll him over onto his back. When he goes to hump you or others, you may have to make him sit, down, and roll him over. Sarah, you did your reading, went to classes, did homework...  You just let it get out of control for awhile.  Take charge again and your dog will respect you for it.  You will be fine. Keep me posted on how things work out, or write if you have any trouble. Thanks. Regards, Susan