I’ve watched and rewatched that lesson, Tuomo has done a fantastic job ! Also i’m very interested in that lesson, and that also might be usefull to copy some of his vocings for arrangement, and playing. At 13:05 in the video, he plays a Bbo7 and a Bbmaj7, instead of only playing a Bbmaj7, why ?
Aside from the harmony topics @Hayden listed, I can recommend working on rhythm as well, and in particular to become comfortable with hemiola in your melodic improvisation. Bill Evans often said that he worked hard to liberate his melodic improvisation from “the bar line,” and I know from my own attempts that it’s challenging to do.
Start with simple melodic phrases that you choose from your own improvisations or that you transcribe from Evans’ examples, and practice playing them starting on every eighth note (every half beat) as you comp for yourself and keep steady time with a simple, fitting chord progression in the left hand.
Having his mind work with great facility “across the bar lines” is a hallmark of Bill Evans’s playing, and the better you are at this, the more of his sound you’ll have access to in your own improv.