top off

Hi Everyone, No, I'm not an expert, and yes, I only watched the first 1/3 of a Heron's Bonsai video on pruning/wiring my first spruce before giving it a shot. Obligatory "I butchered it" and "I know it looks horrible" - please help me! I accidentally topped the tree before reading that this...

I have a very old liquidambar that stopped producing low branches. How do I get more lower branches? Can it handle topping off? I can also air layer the top if the bottom will grow new branches.