fiberglass pool issues need advice

hello all newbe on the forum

recently I have purchased one of those forecloser homes in south florida to live in. The house is good and the pool
is a disaster. Let me start with that when I signed contract for house the pool was drained which they do a lot over here when the house is abandoned. So when I got the house the pool was filled and not running . Also noticed that every single day the water level is dropping about 2 inches . when pump was running it dropped about a feet in an hour . after taking a closer look and some research I have find out that this is a fiberglass pool made by gold key pools
so here is what my suprise was the pool is finished with diamond brite and is cracking everywhere. so I got myself a small jack hammer and cleaned close to half all diamondbrite. it is a lot of work. after that I plan to sand all surface and put a layer of fiberglass and then gelcoat. I still have not find where the leak is , water level already past returns and light but it is still dropping so I would say it must be the main drain but when pump was running that would suggest it is in the return line . I have find some pictures from the seventies that looks like my pool .
the company went out of business in early nineies . I will post some pictures where I am in progress but in the mean time if you all have any advice or thaughts it is greatly appreciated. please exuse my english I can speak better then write