It's a shame you had no reply from social services. Could you try again? If you are worried that DS and GF might get pregnant, they might take a bit more notice, maybe?
I'm glad you've found the work counselling service, and that it's helpful for you. Agree with PP that the teenage years can be horrendous and you need support from somewhere, for both of your sakes.
Also agree with PP that the DS you remember is still in there underneath the hormones and acting out, and you will find a way to bring your relationship back to a harmonious one as you're willing to keep trying. Consistency and boundaries are important now, even more than the toddler years. I was unprepared but have come to accept that these teenage years actually require more input than the toddler years did, for me anyway.
Whatever happens, you must look after yourself. The boundaries must include you always feeling safe in your own home and environment so, if you feel he is aggressive or has aggressive outbursts, it is not acceptable for these to be threatening or intimidating for you. One piece of advice I received form a friend who works with 'troubled' and 'difficult' teens is to give them an arena to express their more physical outbursts of emotion in a safe way. Examples she gave were martial arts, gym generally, and also a box of cheap crockery from car boot or similar that they have a reasonably safe place to do what they want with, like a wall in the garden where they can throw the plates to release anger, and then help bring themselves back into a calm state by sweeping them up and wrapping in newspaper.
Hang on in there.