Gray and Fluffy

Hi

I have learned a lot from reading other posts, but I still have a couple of questions. I have been using the BBB method this year, and have saved lots of $ (thanks guys!) and the pool seems nearly perfect, and less work than previous years...but a couple of questions. Here are my pool stats:
Inground pool, vinyl liner, about 22,000 gal, two eyeball returns, one skimmer, one main drain, sand filter, gets nearly a full day of sun, usually shut the pump off overnight unless shocking the pool
FC 3ppm
TC 3ppm
CC 0 ppm
pH 7.3
hardness 285 ppm
alk 89 ppm
cyan acid 20 ppm

I use the walmart test kit, and bring a sample to the pool store every couple of weeks because I'm curious how our results compare and to see what the cc is. They usually say "hey your water is perfect" :) , I've only bought $16 worth of pool toys there this year! :)

1. When I go out in the am to turn on the pump, there is often grey fluffy stuff accumulated in the corners and seams of the "ramp" that leads to the deep end. I usually vac it out, or sometimes sweep it to the main drain. Is this live algae, dead algae or something else? The pool has a tree close by, and with the absolute ton of rain we've gotten here in RI, I wasn't sure if it was just dirt or pollen washing off the tree. I don't like to vac so often, do I just need to give it a good shock?

2. I usually keep the valve controlling the suction on about 75% skimmer/25% main drain. Swimming down to the bottom and feeling the suction, this seems very light from the main drain. We are a small family, with a young daughter, so we don't create a lot of turbulance in the pool, is that gray stuff accumulating because there isn't enough filtration of the water at the bottom of the pool? Should I increase the main drain percentage? What is a good balance to keep between skimmer/main drain?

3. The filter pressure is usually around 10psi. When it gets to around 18psi (or I have vac a lot of gunk) I backwash the filter. We bought this house with this pool about 3 yr ago without any experience. I backwash by turning the handle to backwash, watch the sightglass get cloudy, then get clear, then continue backwash about 30 sec to 1 min after clearing, then rinse about 30 sec, then back to filter setting. Is this correct? Is the gray stuff in the pool because I am not backwashing correctly or completely?

Although this is a long post, I really feel my water quality is quite good, nice and clear, I just hate seeing that little bit of gray stuff on the bottom. This year (year 3) has been a breeze compared to year 1 on baquacil ($$ and cloudy), year 2 converting from baquacil to chlorine ($$, cloudy, lots of work converting and replacing sand). Thanks for any input
Chris