If at all possible start the T-58 in the low 60s and let it naturally rise. It gets bubblegummy if you start in the high 60s and the fermentation goes into the mid 70s and higher. It attenuates pretty quickly (2-4 days), but let it go two weeks anyway, you will get better results.
Although the bubblegum may actually work pretty nicely with the Galaxy hops. Either way, you’ll make tasty beer, and you can always dial in the recipe the next time you brew it up.
A trick I use is to match the percentage of sugar with the percentage of crystal malts. This seems to give me the attenuation I am looking for while keeping the maltiness and mouthfeel. So maybe go 5% sugar. I don’t think you will get much of anything if you don’t bump it up to 5% anyway.