Sounds like your diet is going in the right direction. By the way, red meat isn't fattening, it's the potatoes, rice, etc, which puff out the midsection. If you don't have any allergies to it, go ahead and enjoy a good steak, it's healthy. If you're trying to lose fat, the calories in meat might make it hard to meet your quota, otherwise I wouldn't worry.
For severe fat loss, I recommend the "Paleo" diet. Here's a link to everything you could want to know about it, and then some:
For weight lifting, you need to get the protein intake up over the basic diet.
Do you see an orthopedic doctor for the back? Can he set up with exercises that will get your core into shape? That's how I did it, and it worked fine. Or maybe a personal trainer. You probably noticed we do the big lifts here - squat, bench, deadlift, overhead press, etc - those give us the most bang for the buck. Once you can deadlift 200 lbs or more, you'll be picking up your grandchildren with ease.