Start practising in a narrow 'tunnel like' space with your back against a wall/fence/hedge so he can't go past or around you. The perfect no-distraction place is the hallway of your house with all doors shut or if you have a path around the side of the house or something like that. Give him heaps of praise and play when he comes right back to you, getting down to his level by sitting, kneeling or even lying down and encouraging him to jump all over you on his return all work well at the start - it's all about getting the bond going between you and him - and then you can progress to standing up and having him come to sit at your feet. You could even build a narrow retrieving run in your garden with a length of cheap fencing - these are really useful because as he gets older you can add in small obstacles which he has to jump to get back to you which is good working practice.
As for being reluctant to give up the dummy I would take the pressure off him on this for a while. At his age and training stage one or two retrieves a couple of times a week are plenty and when you send him for a retrieve encourage him to come back to you as above - sit or kneel down and speak to him softly and encouragingly - and let him hold on to his prize, even ask him to walk around with you while still holding it and don't try to take it off him straight away - whatever you do you don't want to put him off retrieving or coming back to you, he's still young and you have plenty of time to work on his presenting later, at the moment the most important thing is to keep him keen and keep the bond and trust between you and him. You can practise his 'give/leave' command at other times with other toys when he's not in retrieving mode and give him plenty of praise and do toy exchanges etc. Don't use food though or you may end up encouraging him to spit out the dummy in anticipation.
