Although it was early the heart already hung heavy in the air.
The rhyme scheme is ABAAB; the rhymes are strict and masculine, with the notable exception of the last line (we do not usually stress the There are four stressed syllables per line, varying on an iambic tetrameter base.
Run on sentence. A comma splice is a sentence that uses a comma when it should instead be either a colon, semicolon, or conjunction, and there is no comma so that is wrong. There should also be a period between bed and he. Here is what the complete senctwnces would look like: My dog sleeps beside my bed. He wakes me up in the middle of the night to let him out.