Get a new guage. That one's done.

You need to keep your FC above 10 with 0 CYA.

Pucks don't dissolve fast enough to fight algae. You can use granular dichlor to bring your FC to shock level and add CYA at the same time. Trouble is, as your CYA increases so will your target shock value.

If you use nothing but dichlor to bring up your CYA, according to The Pool Calculator, you'll need 5 or 6 pounds of dichlor to reach a CYA between 40 and 50. Each pound of dichlor will raise your FC by almost 9ppm and your CYA by 8ppm.

If you want to do this, buy the dichlor and some borax as dichlor will lower your pH.

Run the filter 24x7.
Be sure there's no chemicals (other than pool water) in the filter or anywhere between the skimmer and the filter.
Add a half pound of dichlor slowly to skimmer.
Test FC, CC, and pH as often as possible, at least twice a day.
Each time FC gets back near 10, add another half pound.
Whenever pH gets near the bottom of your test, adjust it up with Borax.
After 1.5 lbs total dichlor, add another half pound each time FC gets near 12.
After 3.5 lbs total dichlor, add another half pound each time FC gets near 15.
After 5 or 6 pounds total dichlor, switch to chlorinating with bleach and maintain your shock value of 15.
If at any time during this process, your water clears up, and you have 0 ppm(or nearly 0) CC, and you lose less than 1ppm FC from sundown to sunup, maintain shock value for one more day then let the FC drift down to normal levels for your CYA level as found in Ben's Best Guess Chart. Test for CYA after fourth pound of dichlor to be sure we aren't way off with the pool size.