Amplid splitboard, Phantom Bindings, Atomic Blackland
^OP I'd put you on a 148-152, with a mid flex board intermediate/advanced board. Reason being ur note being strong. A mid flex will help to mitigate the challenge with small feet. To help with small feet, you want stiff well fitting boots to assist in engaging your edges. It might be hard to find stiff small boots... so get some tongue stiffeners.At 135-140 ish lbs you should probbaly ride a 148-150 mid soft board. 138 does sound a little small for your weight.
As for boot sizing, you can probbaly find some more neutral looking woman's boots and bindings.