How do I reset or adjust the UiElement size when changing screens?

Question

This is my code. What I want is for, inside the tab control, within the tab item, the scroll viewer to adapt to the exact size of the grid. When I open the program, the size is correct. When I drag the application to another, larger screen, the size adjusts correctly. However, when I return to the smaller screen, the size remains as it was on the larger screen.

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="2*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <StackPanel...>

        <TabControl Grid.Row="1" Style="{DynamicResource TabControlDetailsView}" Margin="25,0,30,0" Focusable="False">
            <TabItem Header="Description">
                <Border Background="Black">
                    <Grid Margin="20" MaxHeight="{x:Static sys:Double.PositiveInfinity}">
                        <ScrollViewer VerticalScrollBarVisibility="Auto" Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Grid}}">
                             <HtmlTextView Content/>
                        </ScrollViewer>
                    </Grid>
                </Border>
            </TabItem>
        </TabControl>

        <Grid Grid.Row="2"...>
    </Grid>

    <Grid Grid.Column="1"...>
</Grid>

I also tried something simpler, like setting the Height of the ScrollViewer equal to that of the Grid, using Height='{Binding ElementName=test, Path=ActualHeight}'. It gave the same result as the code above. I also attempted to follow an online example by using a <RowDefinition Height="*"/> but it didn't work. In that case, the content of the HTML expanded completely, and the ScrollViewer didn't function.

I don't want to set a MaxHeight because I want the Grid and the ScrollViewer to adapt to the available space on the user's screen. If I set the MaxHeight, when switching to the larger screen, there's a large empty space above and below the Grid. And even though MaxHeight is a more feasible option, it wouldn't work for the layout idea I have in mind because my concept involves a page without a ScrollViewer, where the user chooses the information tab and it appears on the page only in the available space.

How do I make this grid, scroll viewer adapt to occupy only the available space, adjusting the size when switching screens?