15 pounds? That's all? And that's too heavy for you?? I guess my question for you is why did you buy a heavy Surly Disk Trucker and two saddle bags if you're not going to carry a load? That makes no sense to me, you could have bought a lightweight gravel bike since you're not going to carry a load, attach a large handlebar bag and call it a day; or for that matter, since you're on the road, bought a lightweight road bike.
Whatever.
One of the suggestions of using a headlight as a tail light is not legal anywhere in the US, and could land you a ticket; only a red tail light is legal to be used on the back of a bike, or any other method of conveyance.
If you don't need rain pants then ditch them. Wool sweater and socks, ditch them.
A large handlebar bag like the 8-liter Topeak Tourguide DX, or a large saddle bag like either the 10 liters or 15 liter Topeak Backloader, which are both waterproof unlike the handlebar bag I mentioned, will reduce the weight of how much your two panniers weigh plus the weight of the rack significantly. Of course, you don't have to get the Topeak brand, but Topeak makes the largest and best handlebar bag with a map cover; but in saddle bags, there are a lot of brands out there that carry similar quality bags, I just know that Topeak stands behind their products, I can't vouch for others. That Topeak Backloader simply hooks onto the seat post and seat rails, no need for racks. The handlebar bag is a bit of an inconvenience for attaching anything to the handlebar, which means you would have to get a handlebar riser so you can attach stuff to it; so in your situation, I can't recommend the handlebar bag system, but I mentioned it because maybe you might prefer it for your needs, but doubtful.
So if you want to reduce the most amount of weight, get rid of the panniers and rack.