My hcg level was about 1500 at 21dpo but it is different for everyone.
They should be able to see a gestation sac at levels over 1500. Good luck to you and congrats.
I was always told that HCG levels cannot tell you how far along you are, because they vary so much from person to person, the "normal" range is vast. The only importance of HCG is that it should double every 2-3 days. As far as I am aware you need an ultrasound to tell you how far along you are.