Bees are very energy conscious, they will usually cap comb when it is ripe. Towards fall however, they tend to sometimes not cap honey even though it may be ripe, especially if they feel they will be using it shortly. You could do a simple shake test of the uncapped honey to see if any comes out, and if not you are probably relatively safe to harvest it, particularly if you use it shortly thereafter.
A refractometer will tell you for sure whether it is honey that is ripe or not.
In the mean time, if that top deep is plugged out I would seriously consider adding another deep between the two, but like Iddee said, first find out what's in that bottom deep.