my 91 si also makes a light knock sound. Most likely nothing to worry about, could be an injector getting a bit noisy, could be one or two valve lifters just a little bit out of spec, could be one spark plug hitting just a little bit early. Nothing that's gonna cause damage (least that's what the Honda specialists told me)

very unlikely that your engine skipped a timing belt tooth. If that happened you'd feel a noticable power loss at some point in your power band (depending on which way it skipped). The smoking at WOT is probably valve guide and piston ring wear letting just a little bit of oil past the seal. To be expected of a high-miles, well-worn Honda engine. Try putting some Lucas Oil in your oil next time you do an oil change. If it's burning more than a quart of oil in 500 miles, put in one whole quart of Lucas oil, and if it's less than that, just put in a half quart of Lucas Oil. You can get it at Napa Auto Parts, and I'm sure lots of other parts stores, depending on which stores you have in your area.