I don't know, to be honest (but I'd like to help). Would you be better off doing a different form of cardio, lower intensity but longer lasting (such as swimming)? By way of comparison, my workout plan has about 30 minutes of cardio (15 min crosstrainer, 10 min stepper, set piece rowing; sometimes I swap this out and go swimming, although I don't time this) and I try to get to the gym 4 days a week (where I also do weights)- although don't assume what's good for me is good for you.
In terms of what you can do, it's a question of what you can fit in with the weightlifting without compromising things (not just talking about time, also energy). You don't want to injure yourself or compromise your resistance training. Also keep in mind from everything I've read that if you're losing weight, your hypertrophy will probably be minimal (most people can't build muscle in a calorie deficit). For that reason I'm working on losing the weight and then thinking about shape (I am weight training, but with an idea that I'll evaluate size and possibly put myself into a calorie surplus to develop definition when I get down to goal weight- this will mean some fat gains which I'll then diet to lose).
I gather too much cardio can be pointless (you're better off working yourself harder rather than being on a treadmill for an hour), but I don't know about "bad".
The only other thing I would consider is how your body will respond to extra work- do you have any joint problems or are you overweight enough that that might conceivably be a problem if you up your working out? (Nothing personal, just something to consider)
Hopefully someone who knows some more about this stuff will come and give you some better advice.
