Desperate times call for desperate measures?

my 3 year old son is the pickiest eater in the world! he has a very small and select menu of foods that he will eat, and it really has me concerned. this is all that he will eat, chocolate poptarts, oatmeal with cinammon in it, cheerios (sometimes) pancakes (sometimes) beef hot dogs without the bun, grilled cheese (sometimes i can sneak turkey on to it and he will eat it) any kind of chicken nuggets, macaroni and cheese, french fries, spaghetti and meat, yogurt, and chocolate pudding, ice cream, wheat thin crackers, any kind of potatoe chips, he will also drink tons of whole white milk, apple juice, and soda but his dad gives him that when i am not around. and then he also takes 1 flintstone vitamin every morning. but then, he also has days when i can't hardly get him to take a bite of anything except for chocolate. as a matter of fact, in the past 2 days with the exception of a few chicken nuggets all i have been able to get him to eat is chocolate poptarts, and as a result he woke up early this morning throwing up, i guess because he has nothing on his stomach. he has no fever and otherwise acts like he feels fine. i am at my wits end. and my husband and i differ in our thoughts on how to handle this very huge problem. he says as long as he is eating something that we need to feed him what he likes to eat. i say, i don't want to take everything that he likes cold turkey, but i do want to cut it back a considerable amount so that when hungry he will have no choice but to eat more healthier food that i try to get him to eat.. i am due to go do the grocery shopping this morning and i have a mind to just go through and not buy any of the junk that he likes to eat, but instead buy him healtier choices of foods and snacks. the way i see it, if it's not even in the house not only does he have to settle for what is in the house, but also, if it's not here then my husband can't cave and give in to his junk food habits. however what if i can't get him to eat the healthy foods that i buy? he can't not eat anything obviously right? thats whats made him sick this a.m... i have no idea what to do.. i have even read up on this and have done all of the other suggestions, he sits at the table for every meal and snack in his booster seat, when served he normally gets a helping of each healthy food that we are having for our meals, and then a food that he likes is also on his plate to, i try to give him choices and we try to encourage him to at least take 1 bite of each of the other foods to. sometimes it works, sometimes it does not... please, i am desperate to get this little guy to eat better. he worries me. especially when he wakes up throwing up because he has not eaten enough, or properly... are there any more tips that i can try? i am desperate and will try anything at this point. thanks.