Hi there, sounds like this is his way of controlling you both.

I would like to suggest you start with the food issue first. Assuming you are all sitting down to eat together, tell your step son that he may get down from the table once he has eaten 1 spoon/fork of potato and two spoons/forks of beans and one piece of meat. Join in with him and say "look I'll eat this bit if you eat that bit" (children are best led by example) then praise him like mad when he does it. Try not to be harsh or angry with him because there is no way he will respond to that but keep your tone light.

Once (hopefully) you have the meal thing sorted out you can use a slightly different tactic with other issues,
e g "Come and put your coat on"
"No"
"Put your coat on then we can go and play in the park"
"No"
"I am going to ask you once more and if you don't come and put on your coat you will go and sit on the naughty step"
If he still refuses take him by the hand and sit him for 5 minutes (1 year for each year of his life) on a designated 'naughty step/chair etc. After 5 minutes return to him and ask for an apology and then ask him to put on his coat again. If he still refuses return him to the naughty chair again. Eventually if he agrees and puts on his coat give him loads of praise and big hugs etc then take him to the park (or what ever).
There is an excellent TV programme that runs in England called 'Supernanny' and it has just completed a series based in the US, if you can look out for it it will give you invaluable advise on how to handle difficult children.

Good luck.

I think i may be able to help with the food issue. Never give in to a child when he refuses to eat something simply take it away. Bribery only works for so long so what i find best is when you make a meal try something like cottage pie coz it has mash potato. Put it in front of him and don't really say anything if he makes a fuss just carry on eating yours. The best way is not to fuss over them as they know they will get your attention be it good or bad by not eating. Eventually he will probably try a bit (maybe not the first day or the second) Just whatever you do don't give up and don't give him other foods to substitute what he won't eat. If he refuses to eat he simply has nothing. Seems harsh i know but if they are really hungry they will eat.