> I just sanded the deck and was wondering if it matters if you hit the
> fiberglass?

With 6 oz. or even 4 oz. glass, sanding into it is not a bid deal so long as you don't sand through it. Most folks instinctively stop when it gets white and fuzzy, and at that point very little damage has been done.

> On some of the edges the fiberglass is showing, should I
> re-epoxy these areas or can I just varnish over it.

New epoxy should make the edges disappear. Varnish may or may not work, so probably best not to take the risk. Epoxy will only slow you down by a day or two.

> Will the varnish make
> the sanded epoxy transparent again?

When varnishing, most guys sand with progressively finer grits. The big grit does the real work, and the finer grits sand out the scratches left by the bigger grits. Some guys go to 400 or 600 wet/dry at this stage, but I have found that 150 in a random orbital sander leaves scratches that cannot be seen through the topcoat.

> Will the strength be compromised due
> to the top being sanded?

To a limited extent that is true, but unless you sanded through a large area the difference is vanishingly small.

> What should I do?

Take a deep breath, pop open your favorite adult beverage, and relax. Then roll on a THIN coat of epoxy. I'm talking 1-2 oz. for a deck. Let it cure until you can't dent it with thumbnail pressure, and then continue where you left off. You won't be able to see it, and it will never bite you.