241 on open jaw ticket

Yes and Yes

No – you can also book the outbound with the 241 then call and ask BA to add the inbound OR book the inbound separately if you have enough avios and ask BA for half the avios back.

How do you mean, work? Yes you will have 2 PNRs but this is not a problem – in fact it can be a benefit if for any reason you need to cancel one leg.

If you think your outbound seats will be taken before the inbound appear this is a better method than waiting and calling BA to book the entire trip.