It depends upon what your goal is. The airlines really don't care about single hours after the 1000 mark or so, if the airlines are your goal you need to progress to twin time.
If there is enough work on instructing twins at your current location, then the twin thing is a good thing to have. If not then you need a twin charter job - but the instrucing ticket can sometimes help with this.
Yes, I would say that you have enough expierience to instruct in the advanced sequences - if you learn your stuff well, and keep learning.
It is pretty rare for an airline to hire staight off the instructing ranks, but this is because the flying hours/age thing for instructors is usually pretty low. To get, say 2000 hours on twins instructing can take 6-7 years plus, as opposed to 2 years in a solid GA job.
Certainly the airlines have no objections to instructor time (I was an instructor for three years).