Something like that, I think, though I find your habits unduly restrictive. On the other hand, using 'ona' at all isroblematic when there are more than one pluasible nouns before -- a greater likelihood across sentence boundaries. Things like 'ona mije' help. I tend and recommend using 'ni' pronominally for thinks that can be pointed to, either a sentence or an extra
Iinguistic object, not just for anaphora. Back references with 'ni' are pretty much confined to 'tan ni la'
The whole idea of 'pu' introducing subordinate clauses does make me start to think about breaking the order rules a bit, e.g. 'jan meli li utala e Jan mije pu e jan mije [something, I suppose] Jan meli ante li lukin'. The something is a serious problem, though, so I'll drop that whole thing unless 'pu' can play a pronominal role here.