Partially correct. I'll elaborate.
[@Fallenreaper]

1. Correct.
2. Radiim is the technique that increases the flow of adrenaline in his body, increasing speed and strength for a limited time. The ability to stick to the bridge is magical in nature and is allowed by a charm he wears on a bracelet around is ankle. An anklet? It shares its magic with most of the other charms.
3. Yes, grabbed one of his daggers.
4. Basically, when Trixi stepped in with the right and attacked, Nicoli mirrored her action but swung at her head. So, I imagine that the two are very, very close. Almost as if dancing. So it's a very close proximity swing.
5.Attacked with his dagger the moment after he launched his attack, which I imagine would be when about when Trixi's own attack struck.
6. There is pain but Nicoli is disciplined enough to not let is show. You are correct, no broken bones. Nicoli has enchanted leathers over his torso and legs, the strike used one of the two charges it holds. 

Please let me know if you have anymore questions. :)