2 problems

Question
Dear Labman,
First problem:
My five month old lab isn't growing properly.She is too thin and her ribs are showin.When i first got her i fed her dog food(kible). She was eating only about one serving per day. So i decided to feed her house food like tuna with bread,chicken with rice and veggies etc.. Even with this change she ate a little more but she's not getting chubbier.Then i changed the vet and he gave her a check up i was told she was fine.But he insisted that i use dog food for better nutrition, so i bought her a different kind then the one i used before (Growing puppy formula) + vitamin pills.Its been a week now but she's still only eating about 2 servings per day with the right amount of serving. Nevertheless she's supposed to eat 3 servings\day.Anyhow she weighs about 10 kilos at 5 months of age.
Second problem:
My lab which is a female is too "lovy duvy" with strangers. I want her to bee more protective of me and my place.Also one time i made her attack a cat which injured her a little and all she did was bark only.Does this behaviour make her a sissy. she's not shy but i want her to have a stronger more aggressive personality. She's so pampered that even when she eats she has to keep on comming back to me between bites of food for affection. Is that normal? So anyhow as i said i want her to be more aggresive especially towards strangers. I'm crating her now for the past two days with no strangers or visitors to interact with. Just me. I can't afford to send her for training. I even bought numerous books just to learn how to solve this problem but they were useless. Please just give a solution i can try and no more books to read.
Thankyou so much and sorry for this lenghty explanation..  

Answer
I am slow answering because I get a server error every time i try to send an answer.  I am trying again.  

Try feeding a concentrated, meat based chow such as Pro Plan, Eukanuba, or Iams.  If cost is a factor, try some of the high volume outlets and as for a house brand like Iams.  Most dog will eat al the need, even if it leave them a little thinner than the owners expect.  Here is a good guide to whether she really has a problem, http://www.photolocker.net/images/Labman/proplanc.jpg

Much of my experience is making sure dogs are comfortable around strangers and accept them.  Maybe try having somebody she doesn't know yell at her or even pretend to attack you.  Just don't go too far.  You will be seen as rude, but discourage strangers from petting her.  There are people out there that think they should pet any dog they come across.  Big pain to people with working service dogs.