Bodybuilding cutting advice?

So im cutting and my maintenance is around 3600-3800, i 15 stone and aim to get down to 3.5 stone in 2-3 months. Anyways i can only get 180 grams of protein a day max because i cant afford anymore. For my diet now i dont eat any junk food, fast digesting carbs, apart from in the morning before i go to the gym and after training. My caories for trainig days are 3200-3400 and on rest days i have 2800-3000.
Is the low fast digesting carbs a good idea? Im an ectomorph and have difficulty keeping muscle, my body usually just burns straight though the muscle. My cardio is a slow, long duration, instead of HIT training i did before which i lost a lot of strength and muscle.
Any other tips would be great, remember i am very calorie sensitive in that i can lose muscle fast.