Rob, you won't find many recommendations for "how much" or "how little" to lift because that would vary tremendously between individuals, espcially older individuals. One 70 year old might be very, very frail and in very bad health; another individual might be active, lean and very healthy at 70.
Here's an article by Tom Venuto, who also has a book for older lifters (I haven't read it, but I like Tom Venuto's articles). You might enjoy reading
Entropy - The Disuse Syndrome.
Also, take a look around this website:
combat-aging.com. You might find more information of the type you're looking for.
But the bottom line is that anyone, of any age, begins where they are and progresses from there. If you have specific health issues, then you deal with those. Yes, you may need more time to recover than someone who is younger, but at any age the advice would be to maximize recovery, progress gradually as you are able, etc.
I also have a selection of articles on my hard drive related to training older adults, but none of them are going to give you maximum amounts to lift or not lift and none of them are going to tell you anything about recognizing signs of injuries that is any different from someone at a younger age. Mostly they are studies or articles saying how good for you it is to exercise at any age.