Sounds like a FIXED LOD Expression would help you out here -- take a look at this and let us know how it helps!
There are also some older techniques using Blending and or Table Calcs as a filter, but I tend to go the LOD route these days. https://www.theinformationlab.co.uk/2013/01/14/maintaining-percent-of-total-whilst-filtering/
Happy analyzing with Tableau!
Thank you. It helped Matt