Small 1/2 copper tubing in very old pool wire will not pull , is my only option replacing pool deck and running PVC, wow that would be expensive just for a pool light

Yes that is your only option.

I question copper tuning was used?

I do not know of any copper tubing UL listed to be used as an electrical raceway.

Then I would question the other electrical work done on this pool.


Then abandon the pool light, if the cost is prohibitive.

Pools are nothing but a hole to throw money into anyway, so what is a few more thousand or so dollars.