Will Snoop turn into a Nightmare ?

Snoop is 15 months old. Upto now snoop has been a near perfect dog. he roams the house freely when we are not there never a problem. on walks he listens always good with recall and will approach anyone or any dog. He has always dropped into lay before he plays with a dog sometimes even rolled over. Snoop has never ever been aggressive some times defensive ie barking but never since a pup been aggressive. He has always been abit soft though lacking self belief if i come to the door and he didnt know it was me he would bark but if i opened the door to come in he would run away.

just recently he has been abit cautious in the dark nothing too serious But, last night i was asleep and i let him sleep with me. my mum and dad came back from holiday early hours of the morning. naturally he heard them and started barking and went to the top of the stairs i stayed in bed and he continued to bark and as they came up stairs he ran to the back room (my mum and dads room) and urinated on the bed.

i don't want him to be unhappy and so stressful i don't want a big nasty dog guard dog that will kill a stranger when they walk through the door i don't care. i am a Royal Marine Commando Boxer/MMA fighter i will protect my dog and my house. But i want him to be happy and confident and i think that for him to be happy he should be carrying out his breeds traits ie confidence and protective .

Please any help will be greatly appreciated i will put the time and effort in to correct this.

Tom