Are lay people in Buddhism allowed to teach Buddha Dharma?

Yes of course, anybody can teach and practice Dhamma. It is up o the listners to Judge whether they are teaching the correct things, which is again not an easy task. I think you are doing a wise thing by following dhamma perched by ordained Sangha. Beside, your approach is similar to mine...., I too am following the dhamma perched only by ordained Sangha, for some good reasons...(But I don't deny the fact that there are many good lay buddhist teachers all around the world.)