A good option for cabling those overhead fixtures is with zip cord and plastic sockets. With an 800ASA camera you likely won't need a bunch of 75w bulbs. Might be better to plan on a bigger array of 15 or 25w bulbs so as to create a larger source that is more ambient. You're basically making custom sized christmas lights that you can put your own bulbs into. (If you're really strapped for cash, the large bulb christmas lights wouldn't be a bad idea either if you can find ones that are still incandescent.) If you had a bit more money I'd suggest going to somewhere like Litegear and getting strips of LEDs and doing that as they're dimmable, lightweight and low wattage.
Place a layer of diffusion over a couple of lines of those depending on how big you want your light to be (could you rent a 6x6 or 8x8 of something you like?) and you've got your ambient fixture. You can use the rest of that zip cord to make small extension cords that are easier to hide. You can make a few different circuits or one circuit and attach to a dimmer (or several). Those avenger suction cups should hold something like that no problem. Just use some A-clamps to hold the zip cord to the pin or whatever is on the suction cup. And just keep an eye on them between takes or scenes to make sure they're holding.
I basically did that with the guts of a couple of Kinos and it ends up being a great top source. You can then tack or tape up duvetyne, black wrap, visqueen or hell even black trash bags to tease it off of the walls. I like making the teaser out of small pieces rather than one big piece so it's easier to open up sections of the light depending on blocking and shots. And it's important to make sure it's longer than you think you'll need. Always easier to roll it up and clip it than to add another piece.
I think your best bet is simply to source from practicals and shape with china balls or even bare bulbs if you want something harder and use that toplight as ambiance.
Another option for that ambience is to get your hands on a hazer and just keep a nice level of haze in the room. The light from the practicals or any source that is in front of the lens will light up the atmosphere and provide you with some fill. It gives a much more interesting texture that just using a source but also takes more work to keep consistent. But that could be a cheaper option to look into. Also very much depends on the feel of the movie.
Hope there's something helpful in there.
