First, you need to establish how much carbonate alkalinity your tank uses in a given period. You already have a rough idea of this, because you say your tank's alkalinity dropped by about 2 dKh over the past week. Then, you need to find out how much you would need to dose to bring the carbonate levels back to where they were.
This calculator says it would take 200mL of B-Ionic to get your alkalinity from 7.6 dKh back to 9.5 dKh. This suggests that you would need to dose 200mL to your tank every week to maintain a stable carbonate alkalinity, or about 29mL every day.
Personally, I would start dosing around there and see where your alkalinity goes. Be sure to test daily to see what your alkalinity is doing. If you notice your alkalinity rising higher than you would like, reduce the daily dose. If you notice the alkalinity dropping, increase the dose. If you notice the alkalinity staying stable, then you've found the right dose per day. Keep in mind that all of this relies heavily upon having accurate and working testing equipment. Be sure that your Hanna Checker is functioning properly and that your testing procedure is consistent.
Another thing to consider is the alkalinity of your salt mix. You mentioned you use the blue bucket Red Sea. The alkalinity of this salt should be between 7 dKh and 8 dKh. Keep that in mind when calculating your dosing amounts. If you maintain an alkalinity higher than that of your salt mix, a water change will decrease your alkalinity. If you maintain a lower alkalinity than that of your salt mix, a water change will result in a net increase in alkalinity.
