Yes, deload for DL's.
On the strain you'll have to see how it feels. It is not something you want to mess around with. Read the first part of the injuries thread.
Provided they start light enough most people shouldn't be getting injured on this. But I'm also reading about you heals coming up so there could be problems with major strength imbalances, flexibility imbalances, form problems, things like that.
There is a squat article in the training articles section which is good to read. Having a strain this early on (not that you should get one later either) makes me think you should perhaps drop the Rippetoe for now and go with lighter weights higher reps and get used to the exercises. That's unusual advice for me but hearing about a potential injury I think it's warranted.
Your thinking on the weight training helping with fat loss isn't far off. High intensity full body things really increase fat buring after the fact so they can help in that regard. But the high frequency and intense nature of Rippetoes.....I wouldn't want to be on a caloric deficit with it. It is all about recovery. I'm not saying it's worthless but it will seriously undermine the effectiveness of it.
And are you doing lots of pullups and pushups? Because just losing a certain amount of weight isn't going to guarantee anything
