t (tetex) is a distribution of the TeX/LaTeX typsetting package http://www.latex-project.org/
, it is used most often for typesetting scientific articles or books. It can also be used for letters and other documents (what I do).
tcl/tk is a scripting language (tcl) and it's gui-toolkit (tk)
You don't need this packages.
Slackware's default is a complete installation. If one wants to build a minimal system, this is very difficult and needs a lot of experience. If you install KDE, don't install the kdei series, this are only localization-packages for kde and since you are in the USA you don't need them. You can as well omit y (games). If you don't want to install the desktopenvironment XFCE you can also omit this series. For xap, look which windowmanagers you want to install and remove the others (it's easy with pkgtool after the installation).
As of the n series, you don't need samba and apache, but the other packages from this series are so small that it doesn't hurt to have them installed. Don't uninstall packages from the l series.
If you don't use emacs, uninstall e.