Foam and Oils.... PLEASE HELP

My boss and I inherited the community pool from a long, long life of negligence. As in filter sand has never been swapped out and the filter never cleaned.... the bottom of the pool is crumbling apart, the chemicals were not kept consistent and had perpetually high chlorimines and dissolved solids. we were having issues with the water just being gross, causing skin/eye irritation, etc so. We did a total drain to fix chloramines and dissolved solids and a week later we started getting foam. Chemicals were all still perfect and the water looked good under the foam. On the filter, the influent needle sits about 6 psi above the Effluent and vibrates. Conclusion we reached was the sand needs to be changed out but since the filter has been neglected the veteran pool chemical guy said the company said the filter wouldn't survive a resand and clean. Temporary solution was to feed an enzyme to clear out/eat all the oils trapped in the lines/filter. It worked great at getting all the oils out... too well. It unstuck all the oil/crime that was stuck in there and put it back in the pool creating a thick layer of oils that looked like foam. From what we could gather from online... we think water might be getting into the system as well to create the bubbles. in the areas with out the foam, the water almost looks like its effervescing.... we think the rubber gasket where the pump connects to the line might have a leak because there is definitely a loud sound coming from the area... should the system be quieter?

So the questions we have:
1. should we just keep feeding the enzyme and give it time to eat/break down those oils?
2. is the effervescing coming from the possible leak in the gasket putting air into the sytem or would that be from a chemical reaction to the acid/breaking down concrete?