Lots of people here making general comments and suggestions, so I’ll give some actual examples:
Considering ‘rotate slowly’ doesn’t really mean much at all (slowly is subjective, of course) I can suggest the figure of 2°-2.5° per second of rotation. Be patient with it too, try not to force the nose to unstick.
Usually you would aim to pitch to around 12.5° positive pitch. However, this is not strictly speaking true - on takeoff, we actually pitch to hold a predetermined speed for a given thrust setting.
In other words… You were pretty heavy right. Vr probably would’ve been around 165kts or so and your power setting pretty high, in the region of 95-96% N1. I guess V2 would’ve been about 175kts. We normally aim to climb at V2 + 10-20kts. So for your particular case, after rotating (again, 2-2.5° per second) you would pitch to maintain a speed of about 185-190kts. This is know as V4 (you don’t need to know that bit!) And is what you should climb at until you reach your acceleration height, usually 800ft AGL or 3000ft AGL depending on what noise abatement procedure is used for your particular SID.
Hopefully this clears everything up for you!