Balances on both sides are broken

Thanks for posting. Your pivot shoe looks like a match for our 15-180, which is designed to be compatible with our Series 190 coil spring, 15-186 clip, and 15-182 bushing. These components are sold separately.

Since your sash is 25 pounds, I would agree that one spring per side is not enough. The rule of thumb is to take the weight of the sash and divide it by how many springs support it; in this case, 4. Therefore I would suggest the S190-640 spring along with the 15-181 double spring clip. You will also need an additional 15-182 bushing for the new springs.

Installing coil springs can be a little tricky, I won't lie to you, especially when you're working with more than one spring. It can be difficult to feed the complete assembly into the cutout and even I struggle with it sometimes. There's no trick to it, though; all you need is patience and a steady hand. 

The bushing acts as a kind of cushion between the spring and the posts in the support clip. Those posts are actually too skinny compared to how wide the center of a coil spring is, and the bushing just fills the space so they don't wobble during operation. 

You do need two bushing for each side, yes. You also want to make sure to purchase the 15-181 double clip instead of the 15-186 single clip that you had before. I'm sorry if that was unclear.

I'm afraid we don't offer that kind of service. I'm only able to assist you right here on this page.

I'm not sure what part may be missing in this application. I've named every component used in this assembly. As for how the coil attaches to the pivot shoe, it just screws on. You can reuse your old screws from the original assembly. I do that all the time and they work perfectly well. I promise that the Series 190 is the right part for the job; these are explicitly designed to work with the 15-180 pivot shoe. They don't go on anything else.

Awesome, I'm glad to hear it! Please feel free to reach out if you had any other questions. We're always here to help.