Niddah and Tefillin

Question

Dear Rabbi, I received your niddah booklet last friday and enjoyed it immensely. I had a few questions about it: 1) I noticed there is no mention of a moch dachuk kol bein hashemashot in the book, but I realize that it is a presentation b'kitzur that addresses the ikar hadin. Is there ever a need and/or a preference to do the type of moch mentioned in the shulchan aruch? 2) On the hebrew side of the booklet, when discussing the discovery of a ketem on a colored garment, it says in parentheses "unless it seems to her that this is the beginning of her period." (This qualification is ommitted from the english side.) Is this true about k'tamim in general, that if it is suspected to be an indication of the period, we should be more stringent? 3) Is it ever OK for a woman to to bedikot on the first and seventh days only, when she is very sensitive or has other problems doing daily bedikot for seven days? I have heard people relying on such a heter. 4) My family has the custom of putting on the tefillin shel yad sitting, and then standing for the shel rosh. Is this a legitimate minhag, and should I continue it?