So, in the end, I should just pick a scale that holds the appropriate notes. In this case that would be an D# Minor Scale (which also happens to be the key the entire song is in). Of course, I could probably get away with splitting the "solo" into small bits that use different scales, to avoid ending up playing the same notes over and over again.

I'm still trying to get the right words for the lyrics, but I think I've managed to capture the style I'm aiming for pretty well. So far, it sounds a bit like a mix between "Don't Cry" (GNR) and "Every Rose Has Its Thorn" (Poison). I have the acoustic main rhythm like Every Rose, but with a slightly darker sound like Don't Cry, and overall, I think it sounds quite nice, especially considering I'm still new to writing songs.