The only thing I can say is, any progress is positive, well done. I thing trust building is crucial and not to be rushed. If you offer a finger/treat for him to step up to you must ensure that you do not move your finger during these interactions until trust is consistantly in place, its hard to take a step forward and so easy to take a few steps back. Birds pick up on your mood/anxiety levels even before you realise yourself. If you are finding it a stressful experience during training or wanting to rush it, the bird will realise. Relax, smile, talk softly and let him know its ok, in fact a little excitement in your voice when positive things happen goes a long way. Ive never found clickers, or indeed treats work with Enzo but i think she isnt normal. Enzo prefers a 'good girl' or a beak rub when she does something positive. She understands 'its alright' too.
Of course, constantly read his body language, any sign of a warning or nervousness, back off. A shake is good, thats generally a de-stress action, feathers and wings tight isnt etc.