You shouldn’t lose ground on fin. Changing your stack is usually a bad idea, but in your case I’d do 5 days fin and 1-2 days duty. That way you will never have to worry about losing ground again
Any dose of 0.1mg or higher will work aswell as 1mg fin. Higher doses are for more re-growth. As for the shedding, it’s too complex to say exactly why it’s happening at any given time. The main thing to keep in mind is that the medication will stop your hairloss, don’t worry about shedding and when you decide on a stack, stick with it for at least 1 year before re-evaluating. GL