sides of pool feel like sandpaper

Vinyl liner pool. 17,000 gal. Salt water. Intel Chlor. Last weekend pool was almost clear. Took sample in and was told to add a few things including "shock". I have never used shock before (always shocked with bleach), but for some reason this time I used it (urggg). Woke up the next day and the pool looked terrible. Now this week we have noticed the sides about 3 inches past the waterline has a rough feeling to it. Almost like a fine sandpaper. I took a sample in today and was told my water was great. It is light green, not clear. I can see the bottom in the shallow end and I can see the drains at the deep end, but very hazy. I have turned the pump back on (had it on for 48+ hours) and felt like it was doing nothing, so I turned off). Got in the pool today, cleaned the sides with a rag, vacuumed the pool, backwashed, rinsed, added more water and have the pump going and the salt cell going at 40%. My readings at the pool place are:
CYA 42
Tot Chlorine 3.3
Free Chlorine 2.8
pH 7.5
Tat. Alkalinity 117
Adj Total Alk 104
Tot. Hardness 106
Salt 4100
Pool Company is saying I need Scale Inhibitor (several bags at 25.00/bag). Any idea on other things I can do?

+ Don't use the scale inhibitor; don't buy any more chemicals from them. Do NOT add calcium; scale inhibitor; scale remover, alkalinity increaser or decreaser, algicides, etc.

+ Stay away from BioLab "Alex" testing -- it seems to lead to inevitable overdosing. (Which improves dealer sales -- imagine that!)

+ Read about 'sand algae' => http://pool9.net/algae-s/

Check out the pictures, and confirm that this is your problem.

+ Turn your SWCG off; buy 20 gallons of PLAIN 8% store brand bleach; buy a cheapo OTO/phenol red drops kit; begin dosing with 2 gallons each PM; test with OTO in the AM; maintain DARK yellow OTO results, till there's no trace of algae left.

+ Order a K2006 kit; you'll need one => http://pool9.net/test/

+ Read about lowering your alkalinity, which is what you'll need to do => http://pool9.net/alk-step/

+ Read about handling muriatic acid, which you'll need to use => http://pool9.net/ma/

+ Post your pool dimensions; over 50% of pool owners have significantly wrong estimates of their pool's volume.

+ Brush your pool, to remove any algae films. Vacuum to remove debris and any calcium particles that have collected. Do NOT scrub your pool to remove the 'sand', especially if it's a vinyl pool!

Good luck!