There are rules for multiple event types:
- note (note on/off)
- cc (control change)
- prog (program change)
- pbend (pitch bend)
- cpress (channel pressure / aftertouch)
- kpress (polyphonic pressure / aftertouch)
And for each of these types, there is a default rule defined that passes all events for all midi channels unchanged. Now your config starts with "router_clear", which deletes all these default rules and means no midi events will pass at all.
So after clearing all rules and creating your custom ones, you would need to recreate the default rules for all event types that you need. For example, if you want to have the fixed velocity on note events, pass cc and prog events unchanged and drop all the rest, you could do the following:
router_par2 0 127 0 100
Alternatively, as Aere has already mentioned, you could use an external router. But for simple modifications like your fixed velocity, the internal router is definitely a good option.
Yet another option would be to use a Soundfont editor like Polyphone and configure a fixed velocity for all presets you want to play.
All the best