Your approach is perfectly fine.

I tent to leave way more than that in custodial wallets, but that's a matter of preferences. 
Mutiny wallet is brilliant and works well for the non custodial experience on smartphone. Blixt is good too. I used to stick with Phoenix but since the introduction of Splicing they changed some mechanisms such that I'm not fine with that anymore.

Sats related to Nostr always go through custodial cashu wallets for me, because a little bit of privacy and because I like the technology a lot.

Run your node and caahu mint if you can!