I am a single Mom - always have been. My son is 16. And while people will say he is a "Momma's Boy" he is growing into a very independent thinker with his own ideals and ideas. My son was, and remains, on the low end of the height/weight scale. He is only 113 pounds right now, and about 5'4". But he holds himself equally with physically larger teens.
He often sings out "I love you" across the house, and we start, and end, each day with hugs. He will flop on the sofa, still, and snuggle next to me.
He has gladly watched "girl" movies with me. We also watch action movies and we both hate horror movies. If this makes my son "feminine" then so be it. He has a girlfriend who thinks he is the best, and he is kind, caring, and respectful to her.
He has a ton of close guy friends, and would gladly throw down with them if the need arose. He stands up for himself, his friends, and me. And lets no one dictate to him. He acts on his own and is proud of who he is.
I think this is what "manning up" is meant to be.
If you are worried about his self esteem, of his (seeming) fear of everything, talk to his pediatrician about it. You son is only 7 - there is so much little boy still there. He has, maybe, seen more than he should have, but with love, and communication, you can work that out. If you think he needs intervention - then by all means obtain that for him. But, don't worry too much now about the man he will become. I think that you are on the right tract with him now.
Hugs.