Food and walking issues

Question
I adopted a lab/sharpei mix last October and we love him but there are a few things I wish I could understand and change. Biggest problem I have is that he is really scared to go on walks and also really good at slipping out of a harness or collar. Whenever he see's anyone he flips out and does everything he can to get away. He seems to just be scared about everything and anything accept for my husband,the cat, and me.

Another thing that he does a lot is take mouth fulls of food and drop it all over the floor. He is a very picky eater and wants everything to be new. If I buy a brand new flavor of Purina One he will eat the food but after two days he starts dropping the food on the floor and looks at me like I'm starving him. I've tried different brands of food, wet food, adding broth to the dried food but after a few days pass he gets bored with it. On very rare occasions I used to give him a french fry  or something that I had eaten but this made the problem even worse and so I never give him any treats accept for dog biscuits.

Answer
I would stop allowing him to demand new foods.  I would start by feeding him a really top quality food (Innova, Solid Gold, Eagle Pack, Prairie, Nature's Variety, etc.) and then parcel out his dinner.  Leave it down for fifteen minutes.  If he doesn't eat, take the food away for twenty minutes and try again.  If he still doesn't eat, take the food away until the next feeding time, and do not give him any treats instead of dinner.  (Most dogs will not starve for more than three days - during that time, do be sure he has fresh water, which should never be restricted unless your vet tells you to.)  This may sound harsh, but it actually helps your dog view you as a leader, and helps you to know when he really IS off his feed from an illness, for example, to the extent that you would want to take him to the vet.
If he's frightened outdoors, try enticing him along with a piece of cheese or roast beef.  Also, put him in a harness or a martingale collar so that he cannot slip out.  And, make sure you have permanent identification on him (microchip of tattoo) just in case.  
You didn't say how old he is, but puppies are often fearful at certain stages, and then grow out of it.  Other dogs, that may be undersocialized, need remedial training to help them.  One good book on fearful dogs: "The Cautious Canine" by Patricia McConnell.  It's inexpensive and has lots of good hints:-)