- look at a rack that can set the bags back a bit further to help reduce the chance of heel strike. 2 examples are below. I use the bottom one on my touring bike.
https://www.biketiresdirect.com/prod...hoCdj8QAvD_BwE
https://www.amazon.com/Axiom-Journey.../dp/B07BHTSTJL
- buy some panniers. there are all sorts of sizes, prices, and quality. in general, cheaper price = lower quality(lack of durability and/or shorter lifespan). These will cost $40-140 depending on what you choose.
- buy some tiedowns. these allow you to lash your remaining stuff on top of the rack. bungee cords are one option, but arent adjustable. There are lots of adjustable ones that cost $5-10 and work well.
- buy a front handlebar bag. this will let you store a little bit up front so at least not everything is on the rear wheel.
Sure there is a chance your wheels arent up for the task, but the only way to know is to try. Do some day rides around town with full weight on the back and if the wheel is an issue, you are in town to get help/fix it. There is also a chance the wheels are perfectly fine and can handle the weight without issue.
All the weight on the back will make the bike steer differently. Just learn how it feels and adjust. It isnt tough to do.