Bruised toe nails? Get ready for them to fall off. The first two toes are particularly prone to bruising and can be related to shoes being even a 1/2 size too small. I'd make sure you keep your toe nails trimmed short and look into getting a slightly larger pair of shoes. Given that we have 2 1/2 months until the Marathon, you have plenty of time to break in a new pair. Actually, this is the perfect time to get new ones…because come race day, your current shoes will be 2 1/2 months older and have at least 320 more miles on them! Can you believe it?
It is recommended that you replace running shoes every four to six months or 400 miles, depending on body weight and your distance, frequency, etc. I'd suggest buying two pairs of the same shoe now, and alternate them with each run you do. This way, come race day, they're not worn out (only 120 miles each) but they're both broken nicely.
Basically, running shoes come in one of three basic styles: cushioned, stability and motion control. Cushioned shoes are typically recommended for runners with a neutral or high arch who just need cushioning and a shoe that lets their foot move naturally. On the other end of the spectrum are motion control shoes that have a reinforced arch with high density foam built into the arch. These shoes are better for people with collapsed arches/flat feet and will help to control overpronation (collapse of the arch during running). Stability shoes are a blend of motion control and cushioning for those that might be mild overpronators, but want more cushioning/less support.
If your current shoes are working for you, then don't rock the boat, stick with what works. If you're not sure, then visit one of the many great running specialty stores in the area or feel free to contact me. They'll be able to evaluate your foot type and gait pattern and make some recommendations. Bottom line, it should be comfortable! Run easy!