Hey Tim,
I'm sure other more experienced forum members may provide better guidance, but as a newbie I'll take a stab at this for you.
You clearly still have organics (algae) that need killing off, based on your CC level of 2. This means you need to SHOCK the pool - which as is constantly preached on this forum, is a process, not a product nor a finite timing of activities. You need to get your chlorine level WAY UP to somewhere around 24 or perhaps higher (depending upon CYA levels) and keep it at that level until an overnight chlorine loss test shows that you no longer have any chloramines. This could mean adding chlorine every hour if necessary to maintain that FC level, as it gets used up by sunlight and the algae it is fighting.
Can I ask what product you are using for chlorine? Are you adding household bleach or liquid chlorine, or some type of dichlor or trichlor product? The fact that you state the black dot never disappears on your CYA test would seem to indicate that your CYA level really is at zero, and therefore your chlorine is not stabilized in any way and is getting used up by sunlight faster than it can attack the algae. You need to get your CYA level up - I think to somewhere in the range of 30-60. You do this by adding stabilizer. Once you've gotten your CYA level up a bit, the chlorine you add won't dissipate so rapidly, and the shock process will have a better effect.
As for how much chlorine to be adding, based on your FC level of 8 and assuming a shock level of 24, and your 8,000 gallon volume, you need to add at least 2 gallons and 1 cup of 6% chlorine...and then keep it at that level - adding more chlorine as needed.
You can check my calculations and get additional calculations as you go through the shock process from the Pool Calculator, which is referenced on this forum in many places. Be sure to check out Pool School for additional info, especially on how to shock a pool.
Finally, in one of your earlier posts you were talking about turning off your pump/filter. As long as you are in the shocking process, your pump/filter needs to run 24/7 for 2 reasons - 1) to filter out the algae as it is being killed off, and 2) to circulate the chlorine you are adding. Never add chlorine without the pump running or the chlorine won't be able to circulate properly.
Hope this helps a bit, and hopefully the experts on this site will provide additional guidance and/or correct me if I'm wrong on anything I just advised you of.
Good luck!! Let us know how you make out.
Tim