How to implement dynamic "Ratio of Totals" calculation in Freedom UI Dashboards (Filtering Issue)

Current Setup:

I am working in Freedom UI. Currently, I have a KPI called "Margin per Liter (Excl. VAT)". It is calculated via a Business Process that:

1. Sums up the "Margin without VAT" for all orders.
2. Sums up the "Quantity (Liters)" for all orders.
3. Divides the first sum by the second.
4. The Problem: The result is saved into a specific field within a single "dummy" Order record.

The Issue:

Since the value is pre-calculated and stored statically in a record, the Dashboard indicator does not react to Quick Filters (Period, Owner, etc.). It always shows the same total regardless of the filters applied on the page.

Goal:

I need the dashboard to calculate this ratio dynamically: $\sum(\text{Margin}) / \sum(\text{Liters})$. It must recalculate every time a user changes the filter (e.g., to see the margin per liter for a specific manager or last month).

Questions:

1. How can I set up a "Ratio of Sums" in Freedom UI without using a background Business Process?
2. Is there a way to use the "Formula" source in the Indicator widget to divide two different aggregated sums while maintaining filter context?
3. What is the best practice for such "weighted average" metrics in Freedom UI to keep them responsive to page filters?