I suggest a different way to deal with the Know-It-All: encourage him to Know It All. Show him that you are grateful for his expertise. Ask him questions. Defer to him on the little things ("John, do you think we should offer Splenda along with the coffee, or just sugar and Sweet-n-Low? ... Thanks, I knew you'd know the best thing to do!"), ask him if he would help the less experienced techies in setting up makeup stands, or leading warm-ups, or looping cable. Give him helpful tasks that let him talk about his amazing talents and abilities. This will keep him busy and out of your way. This comes from one of my favorite life philosophies - "If you don't know what to say, ask someone about themselves. They will think you are a brilliant conversationalist." If you help people feel clever, they will enjoy working with you. Of course, keep yourself master of your own kingdom and don't encourage him to infringe on SM duties. I think this will be way more effective than the stern talking-to. He needs validation, so validate him. It will mean less pain in the end.
As for your significant other, you should definitely explain to him workplace decorum. Have this talk in the theatre - not at home. You might even coordinate a "training night" where you explain before you go to the theatre that you are about to go on the job (and he is, too). Ask him to go out for a "date" - just a drink or whatever - after rehearsal. Then, be perfectly professional in rehearsal. When you go on the date, be sure not to discuss rehearsal or anything. Have fun, be relaxed, be on a date. This careful guidance might help him learn that the lines between work and personal life. Kind of like house training a puppy.