Your points are valid, but I figured a base of knowledge to see where he is starting at wouldn't hurt. Is he drastically underweight and just paranoid about putting on fat? We'll eat 500-700 calories over maintenance with 1g of pro p/lb of BW, get about 20% calories from fat and the rest cabs
Or is he already overweight, wants to gain muscle but not any additional fat? Well he's already taking anabolics, so maybe just do a small 200-300 calories surplus with same protein intake but more like 30-40% calories from fat and the rest from carbs taken pre and post workout.
You're right in the sense that it's largely trial and error, and regardless of current stats, the surplus or defect that works isn't going to be some cut and dry answer. But for the sake of a starting point, knowing somebodies stats only helps to paint the picture. Anyways...I digress, and agree; start low at like 200+, play with your macros, and adjust as needed every 3-4 weeks