The reason you can't maintain a FC level is because ammonia almost immediately consumes the bleach, hence no FC. Bacteria, not algae, in your pool is converting your CYA into ammonia. This would explain the drop of your CYA over the winter. Typically with a CYA of 150 you would have to drain 60 -75 % of your pool and refill with freshwater to start the TFP method. The good news is the CYA is getting destroyed by bacteria, the bad news is the product of ammonia, the enemy of FC, so to speak. Make sense?
Here is what I would do:
1. Go get a ton of bleach...you could get a shovel and a plastic tarp if you want to have some fun, LOL!
2. Recheck all your levels pH, CYA, FC, CC, ALK, CH. Post a baseline set of numbers.
3. Based on that baseline get your pH to 7.2.
4. Assuming your CYA is 30/40 assume a shock level of 16. If your CYA is different use the corresponding shock level. See CYA/FC chart in Pool School.
5 Dump in bleach to raise your FC to 16.
6. Waiting 15 -20 minutes test for FC. If it is very low, like 0 - 2. Repeat this step until your FC starts to hold at 16. This may take some time, keep at it until your FC holds.
7. Once you get a shock level FC reading (16), start dancing!
8. Wait 2 hours and test your FC again. If your FC drops use pool math to get that level back to 16.
9. At this point you can do a normal SLAM until completion!