The spring comes out of the ground 20 ft before flowing into the lake. Wouldn't that kinda be like well water?
I suspect he saw the rate of "60 GPM" in your OP, or in a reply, and thought you were talking about a well, rather than a spring.
Either way, his reply is solid. Your pond water will be "risky" for your fish with that apparently very low alkalinity.
Here is a link to a good primer on pond chemistry.
Understanding Water QualityImproving your pond water chemistry is going to cost some significant money. IMO, you need confirmation of your test results - probably using a professional resource.
Then come back and get some advice on the best methods of treating your new pond.