Sealing / finishing plywood  

You can
do better than that: you can stabilize and "heal" the damages already present, before refinishing. Finish alone can't entirely prevent the damaging effects of heat, moisture or rough use -- much less heal existing damage.
In essence, anything that moves now should be nailed down with glue. In many cases this can be accomplished without clamps. To get the glue all the way into crevices, gently pry the plies apart with something wedge-shaped, then introduce glue with a toothpick, slip of paper, or similar implement. Then stretch masking tape over the "wound," or apply clamps over plastic food wrap (so the glue doesn't stick to -- or get discolored by -- a metal clamp).

Hi SDR
Thanks for your suggestions. I have already begun to glue some of the separations, using binder clips as clamps. After this stage, I do plan on sanding it some and then sealing. Do you have any recommendations for that?
Thanks again.

Finish
is my weak point. Everything I've built has been professionally lacquered, pretty much. Some say shellac, others like oil, wax. . .
There's been some discussion here previously. Maybe look for that, and see what makes sense to you. I've put Deft lacquer on some home-made stuff (pieces for my apartment). It looks and feels good, and you can brush it on -- 3 coats in one day and you're done. But it doesn't hold up well to water. . .

I am thinking
Just a polyurethane clear coat to seal it. Hope someone else may chime in. Thanks again!

Polyurethane sounds like a good idea,
especially for a seat.
I lean toward satin-finish poly. If you choose satin just make sure you stir it really well-- the substance that settles on the bottom of the can is what makes the finish dull, instead of shiny. Without proper stirring, one ends up with a glossy finish.

Finished
I glued, sanded, and sealed the seat, and then covered the top with leather. Not too bad....

Looks sharp!
Looks sharp!

Nice !
A leather surface could cover a multitude of sins, too -- like through-bolts and screw holes in DCWs ? And you don't see it that often. How many chairs have this as the original finish ? Great idea.

brilliant.
Looks great and i could not think of a better solution for your chair.

Thanks guys
For your comments and for the suggestions to begin with.

lordy
Love that chair. But the hubby forbids it.
Few questions:
What kind of leather did you use?
How did you treat the edges of the leather?
What did you use to adhere it?

Answers
Leather is stained rawhide. I believe the weight is probably 5-6 oz. (about 2-mm thick). I cut the edge with a craft knife and shears so it's not perfect but acceptable. The edge is currently unfinished... I feel like it might smooth out on it's own through regular wear? The leather is glued with Elmer's Craft Bond wood glue. I don't believe the glue itself is that strong, and the bond isn't that strong because the suede side is so rough. Perhaps I should have used more. If the edges do start to come up, I will probably try something stronger.