Don't change too many things at once, from experience it doesn't work long term. I'd recommend changing your approach to almost the exact opposite of what you are planning to do i.e. get your diet and muscle imbalances sorted over the next 6 months then 'go hard' after that. If I was in the same position, as a brief example I would:
First month - concentrate on cutting out the crap in your diet as this alone will likely make you start losing weight. While doing this, start with some very basic single leg exercises (start with bodyweight). You'll want to get both legs to similar strength levels before starting squats/deadlifts as big imbalances will only lead to further injury.
Second month - calculate your TDEE (the amount of calories your body burns) and try and eat 500 calories below this. Start slowly increasing the lower body weights.
.
Fourth month - start squatting just the bar
etc
A few things to note. Don't deadlift, squat and chest press for 3x10 5 days per week. You'll need to split your workouts into appropriate bodypart splits i.e. back and biceps (deads), legs and shoulders (squats) and chest and triceps or 3 full body workouts per week i.e. stronglifts.
Good luck with whatever approach you take, just remember it's a marathon and not a sprint
