Do NOT remove your multiport; just dump a couple of cups into the skimmer.

Also to clarify something (not your water, unfortunately): there is not any definite information that I have found about how to remove soaps and detergents from your pool. I have known of pools to drained as a result. Some detergents (dish soap) are broken down by chlorine; others (laundry detergent) are not. Watermom is giving you generic how-to-clean-up-your-pool advice, not specific how-to-remove-soap advice.

However, very often simply doing your pool the right way for a week or two resolves problems, even when we don't know exactly how the resolution came about.

Adding DE to a sand filter can do two things for you:
#1 - If you see the DE powder shooting back into the pool, via your returns, then you have just discovered that your sand filter (or cartridge filter) needs repairs.
#2 - DE, on top of your sand, will filter out finer material than sand will, AND it will backwash out of your filter freely, hopefully carrying with it what ever it trapped.

On the down side, a sand filter makes a TINY DE filter, so adding DE will greatly shorten the time between backwashing.