Also I have had a long road to find what I need to get freedom and focus. Tried loopers, the octatrack, digital recorders, mpc, sp555, ableton and push, you name it. I found out that with one piece of equipment I cant nail it.
My solution now: mpc live, digitakt, zoom h6 and a looper pedal. In my experience the mpc and digitakt fix each others weak points. The elektron sequencer is great for plocks and sound manipulation live but is a major PITA when you want to compose a song longer than 4 bars and a bit more complex. The mpc sequencer is great at that but is the same major PITA when you want to do lice manipulation. Together I find them way, way better than the octatrack.
As I play keys and guitar I need a looper here there that is foot operated. I also use mics, so there cones the h6: works as mic convertor, a small mixer, recording my sessions in mulititrack and it interfaces well with the computer if i need to. And so do the digitakt and mpc.
Couldnt be happier. Still some limits, bit very close to perfect and the final solution of a 10 year search.
So my 2 cents: id keep the boomerang and digitakt. Get an mpc and maybe a recorder and done.
And my experience eith the octatrack: it does something really well. mangling audio and such and improvisation. But if you wanna record a pteplanned song is is uttetly horribly and a major flow killer.