Hi there, I think you can go either way.
At around the right age (2-4) you can start training.
Alternatively, for DC1, nursery staff said they will start letting you know when they are ready. That is, baby-led First stage - telling you AFTER they are done. Second - telling you during doing the business. Third - Telling you before doing the business. (And then this fourth - and maybe fifth stage which I am just learning about, when they can do all things, including wiping their own bottoms).
The key aspect is consistency. I left my LO without bottoms at every opportunity. Coupled with the nursery also training at the same time, we pretty much were able to do get to stage 3 in 2 weeks. I think LO was around 2 or 3. Another key aspect is that we all agreed LO could communicate with us the need to go.
Perhaps here you need to sit with the dad and ask what he thinks the best approach is and be led this way as he might be the missing piece in this.
Also, not sure if other pp have said this but you may want to leave you LO for 2 or 3 weeks and then start fresh at stage 1. Stage 1 is teaching the language of pottying. So when you are changing the nappy, it's always " ooh great a poo" or "looks like we did a wee". Acknowledging the event. Then a few weeks after that, looking for LO to fill in the blanks when changing nappy. "Ooh, looks like you did a ???" and then say nothing. Eventually they will say "poo" or "wee". then do this for a few weeks. Then if they ever mention that they have just done one, casually say "oh great let's change your nappy". Eventually they will start telling you during. At this point, you want all equipment ready. (Potties / toilet inserts / ladders). And if it happens, it happens.
I hope it all works out for you