Hi Jeroen, I'll try to pass along some feedback:

First, it sounds like he is doing GREAT! Physically he is showing progress and it's still very early so try to be patient, he really is healing!

- Our own anxiety, sometimes it almost feels like it is bothering us more than him at this moment. I.e. will we be able to play fetching a ball or tug of war again which he loved to do. (*)

It's always worse for us! Yes he will be able to do what he loves, but in a modified way. That means taking more breaks, not throwing the ball as far, and don't forget it's equally fun to find new games to play together that are just as much fun.

- Licking lips / hunting non existant flies.

Ah I see that in the video I think. This could be nausea, usually related to antibiotics or other medications, and not enough food in the gut. I noticed you are grinding up his pills in his regular food. Don't do that, it will cause him to avoid his regular meals. Sneak in the pills in other very tasty food he hardly gets, try the cheese trick that Karen showed you.

- sleeping. Last few days he slept more during the day but very little at night as he seems more anxious then (which also meant we had little sleep)

Generally it means his pain management needs adjusting, he might not be getting enough to get him through the night. Based on what you described he is on very low dosages for a dog his size. I recommend asking your veterinarian how to increase his dosages and maybe trying to add in another medication like Amantadineto help him rest better.

- monitoring: as he has a tendency to try to remove the cone or scratch where the wound is we cant let him out of our sight for the time being, Sometimes he also seems to want to scratch with his back paw where his front paw used to be, I guess that may be phantom pain . 

That's a tricky thing for sure! Keep an eye on him. Also, better pain control can help lower his desire to scratch the area. You can also try covering up the area with a baby "onesie" as we call them here in the states (a baby coverall one-piece suit). It doesn't sound like phantom pain based on what you are describing (no crying out, or jumping up for no reason). Generally if you see twitching or attempts to scratch, it just means the nerves that were severed are trying to tell the brain that his leg is still there, and to scratch the area. 

(*) In there it would be great if people have some suggestions on more things to do with him while he has limited physical activity or in case his 'new normal' forces us to rethink some games. 

Generally anything that works his mind instead of his body right now. So interactive brain games , very simple ones, will keep his mind and body tired. The nose work you are describing is a lot of fun! You can hide his kibble in places around his recovery area, like under toys, rolled up in a towel, etc. The previous link has some ideas.

I hope he is having a good day! Keep us posted.