Hi Tamara,
I typically run about 12 to 18 miles per week as my cardio (usually 6 miles per session, 2x to 3x per week, varied types: easy run, tempo run, and speedwork). I am not currently training for a race, but it helps me keep my pace/time. I also cross train with other cardio activities....
Based on your training schedule, it sounds like you may have to do cardio and sts on the same day 2x per week, if you want to workout 6 days per week - which is okay, but you should break out your sessions (I typically do the run in the AM and then weights in the PM). I would recommend doing sts on the same days as your cross train activity and your easy run (so you have enough energy for tempo, speed, and long runs as that is the only thing you would be doing on those days, along with enough energy to get maximum results from sts on days when you double up).
Hope that helps!