Is it possible to write a dependent clause without independent clause?

I want to explain my problems by the following sentences. The following sentences have been taken from Reader's Digest.

"Ed tries to explain why he would want to keep a pile of records he never listens to. "It's just knowing that they're there. That I could listen to them if I wanted to" I reminded him that his turntable doesn't work. "So, actually you can't listen to them." Which reminds me. I pick up the turntable and put it on the designated throw away pile, which I had envisioned at the beginning of this undertaking as a towering, teetering mound engulfing most of our front entryway and portions of the pavement, but is in reality closer in size to the little is in reality closer in size to the little mounds of toenail parings Ed occasionally stacks up on the bedside table."

1) Read again "Which reminds me. I pick up the turntable and put it on the ..............". 'Which' indicates a dependent clause that can not express full sense without main clause. But there are no main clause. It seems that it is an independent clause. Please explain this fact. Would anybody like to give the link of other posts related to this kind of problem?

2) In "but is in reality closer in size ......." what is the subject of auxiliary verb 'is'? It seems that subject is far from 'is', and it will be found in the previous sentences of it. How to find it? If it is possible, please mention the links the post that are related to this problem. You may say some keywords with which I can be able to find the posts related to this problem.