This is just my own opinion, but I don't think you need 50 miles a week of running. I might be mistaken but I believe I read Bob Kennedy (who ran 12:56 for 3K) ran 3:35 for the 1500m at the age of 18 on 35 miles a week. If you had a long run on Sunday and a day off on Friday, you might find that more relaxing, manageable.
In any case, if you live in Canada, I saw some bikes on sale at Sports Experts. The Diadora bicycles lately were on sale with quality Shimano parts. In general, Shimano Tourney < Altus < Acera < Alivio < Deore < Deore SLX or LX < Deore XT.
I'm leaning more on the side of thinking someone who wants to start out might be better off saving a few dollars and getting a bike equipped with Acera which some people find acceptable. There are bikes like the GT Traffic 4.0 or Giant Roam 1 etc.
But, someone had a point here with the cyclocross bike. It's kind of hard to guess what you'd be more comfortable doing. You could really go harder with drop bars on a cyclocross bike. But, I find the upright position of a hybrid more comfortable. And higher-cost hybrids I find have a more aggressive posture which I find a little similar to mountain bikes.
Then you have choices between rigid forks or suspension forks. And disc brakes or V-brakes. If you want lighter, cheaper, longer lasting and in my opinion, less complicated to work on, I'd go with V-brakes and a rigid fork. But that's a personal choice. I won't sermon anyone who wants disc brakes and a suspension fork.
The 700c wheels of a hybrid will get you there faster and allow you to roll on grass easier than 26 inch wheels. But to roll around on trails, you may want 37mm to 42mm tires. Well, enough rambling for me...
