My cat is tired, sleeping in litter box, and has a closed eye. Vet?

I would not operate under the assumption that Jacoby is fine if he is acting unusually. Sleeping in the litter box is typically an indication that cats are trying to hide, or they are too afraid to be apart from the litter box due to an increased urgency to urinate or defecate. If he is struggling to keep one or both of his eyes open he may be weak or in some amount of discomfort. While it is possible he could have a primary ophthalmic issue, given the other problems you have described I do not feel that this is likely. If he is continuing to eat and drink normally, and is not overtly ill, I do not think it is an absolute emergency that you get him into the vet prior to the end of this holiday weekend. But, if the problems persist through this holiday, I would definitely have him examined by the end of Tuesday. Things you might consider doing at home in the mean time just to gather a little information would be to obtain a rectal temperature (above 102.5 is a fever, below 99 is too cold), check his gums for a nice pink color and moist feeling, and pull up on some of his skin by his shoulder to see if it returns to his body quickly. This is a good indication of appropriate hydration status. Hope this makes sense.