Did you take any hydrometer readings yet? If you have the same reading 3 days apart, then you know fermentation is complete & you can think about bottling. Bubbling in the airlock is not a good indication fermentation is complete. Hydrometer readings are the only way to know for sure. If you bottle before fermentation is done, you could end up with bottle bombs.
Also, it's good practice to leave your beer in the primary for an extra 1-2 weeks after fermentation is done to let the yeast clean up any off-flavors that may be present.
The gunk on the lid is krausen. During fermentation as the yeast does it's thing, a layer of foam will appear on top. No biggie...It probably just rose high enough to contact your lid. Anything left on the beer itself will eventually settle out. You might want to rig up a blowoff tube if it got that high so the lid doesn't blow off.
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