I am running cat 5e wire in my basement ceiling, to serve some upstairs rooms. One of the locations requires that I run the wire near a 6" round heating duct for the basement. SHould I be concerned if the wire rests on the duct? Thanks in advance.

Shortly after buying our house, I got fed up with all the coax cabling that ran along the outside of it. So, I took a quick trip into the crawl space to reroute everything down there. While working on this project, I then decided to add coax jacks to 3 rooms, as well as network 4 rooms with cat 5 cabling. Well, after countless hours spent going in and out of this cramped, dusty, sweaty crawl space, let's just say that I was glad when the project was over. Now, It looks like I have to take another trip down there, but I'm looking for your thoughts/recommendations/suggestions since I'm not a seasoned handyman: A few weeks ago during a miserably hot summer day, I was working in the yard and felt an unusually cool wave of air hit my leg. I traced the source to one of the crawl space vents, and deduced that our air conditioner was pushing our expensive cold air into the house, through the cat 5/coax wall jacks, down into the crawl space (through the holes I drilled for these cables), and out the vent into the yard. I bought some foam plates that seal standard electrical outlets from our local hardware store, but I couldn't find anyone who makes these seals for my coax/cat 5 wall jacks. So, do you think I should go back down to the crawl space and spray some sort of sealant up into the holes I drilled for the cabling? If so, what type of sealant should I use? (I'm clueless about this stuff--pretty much everything I learned about handyman stuff is from the good ol' innernet.) Another unrelated question: I needed to secure a tall bookshelf in my baby's room to the wall. I anchored it to 2 studs with braces, but it turns out that one of the studs also has electrical wiring running alongside it into the ceiling. (I inferred this because there is an electrical outlet at the bottom of the stud, and none of our electrical wiring runs down through the crawl space.) Was this a dangerous move to drill and screw into this particular stud? If so, was it a bad idea for a novice homeowner to try pull off? (As you can infer, I survived the attempt, and I don't think I damaged the wire.) Any/all feedback is greatly appreciated. Thanks.