My window span is 140 inches and the rods I ordered came with 4 brackets also, but I only used 3 and it's fine. No bending at all, and I have fairly heavy drapes hanging up. We open and close those drapes a few times each day too. The only issue I had was that the bracket started pulling away from the wall so I had to use longer screws. .

I have had the same situation in one home, reluctant to drill into the doors but, it had to be done so I put some nice rods on them. In the last place we built I had no neighbors behind me for miles and I didnt need blinds or curtains in the public rooms so they were left alone so we could see the beautiful old oaks. If not for that I wouldnt have hesitated to install sheers again. If you need privacy and want curtains you will have to drill holes, just get some nice rods that will compliment the decor. I have installed the small orb toned rods and it looked really nice bc the door handles were the same. Your other option is to hang curtains over the door and extend to just past the door so they are mounted to the wall and pull over the doors for privacy, but thats a pain when you need to get to the door you need to pull the curtains away. Or you could frost the glass for privacy but installing rods for permanent sheers is a better option, top and bottom rods, and theres some beautiful ones out there. I think you will have to bite the bullet and drill if the magnetic rods wont work. The rods if chosen to your liking can compliment the doors and curtains or some can be covered by the curtain so they are not even visible. Heres some pics of styles of curtains on a site I saved because we may be replacing a window with a french door in a bedroom. Here is a link that might be useful: french door styles and curtains

Use a traverse rod with carriers and. hooks. You don't need one with a pulley, you can get one with a wand for opening and closing.

I think the spiral thing would go inside the end of the small diameter piece where you'd join to two together. Put it halfway in there, and then see if you can slide the larger diameter rod over the spiral part that remains sticking out of the other rod part. I have some decorative rod ends that attach like that.