Wow, somebody actually sanded off 1/4". I was thinking oversanding that would sand thru a plywood laminate which is usually less than 1/32".
What's the thickness of the wood that's left? Do you have enough wood left to re-set the screws. If so, try that and make new plugs; Home Depot sells plug cutters - I recommend tapered plugs - H/D sells both. If not, tell me what size you need and how many and I'll cut some and send them to you.
If I had excess or dark varnish, I'd think about stripping it off with a paint stripper (try oven cleaner first - its cheaper). Then use teak cleaner to remove most stains and dark mildew (actually KrazyKlean will take out most of the mildew in the wood). Avoid sanding if possible, as the dark saw dust will get ground into the light wood. Try a wood scraper made for finishing wood - a flat sheet metal peice about 6" long.
