Half a grapefruit has about 4g carb, so just count that in when you're calculating your carb intake. It's not on the allowed foods list on my very-low-carb Atkins-based diet.
Your weight loss is good at present, but don't be surprised if the rate slows down - it frequently does. I wouldn't be losing weight at all on 120g carb daily but that's just me - we are all different! On a low-carb diet you are indeed running on fat and protein. Part of the protein eventually converts to glucose, whereas 100% of the carbs you eat are turned into glucose. I have insulin resistance, which means that my muscle cells are resistant to the action of insulin on glucose, and most of my glucose is stored as fat rather than used for energy. Your training sessions will help with that.
You are not taking statins, but anyone who is should avoid grapefruit/grapefruit juice as it reacts with statins. Google it.
Figures for your lipid profile should ideally be as follows:
Total cholesterol below 5
LDL below 3
HDL above 1.2
Triglycerides below 1.7 and the lower the better. My best ever was 0.65
Total:HDL ratio should be below 5:1 and preferably about 3.5:1. This is a very important figure and the one my GP pays most attention to.
The figures I have listed above are for non-diabetics. "They" seem to want diabetic total cholesterol below 4, though I've no idea how that affects the other figures. I pay most attention to my trigs (1.2) and my Total:HDL ratio (4.3:1). I'd prefer both to be lower, but I've been eating too much carb (for me). My last Total figure was 4.9. My GP is quite happy with everything.
Good luck with reducing your blood lipids by diet. I find the lower my carbs, the better my blood lipid profile.
Viv