Your DH can take 26 weeks leave before the baby's first birthday, but can only claim statutory pay for whatever you've got left from your 39 weeks' pay. So he could have longer than the 15 weeks paid leave you've got left, but would have to take it unpaid.
Yes, your DP can have the remaining 13 weeks of leave and pay - my own DP will be doing this too.
However, I had been hoping to take 4 weeks A/L to allow me a further months leave with him, as a family. But you have to have returned to work and not be on annual leave according to the information I have found. However being a teacher and it being school hols - I'm not sure where you will stand on this one!
I'd suggest you might need specialist advice on this one, although hopefully another teacher who has done the same might come along and let you know if it is possible or not!
But on the face of it, yes, your DP can take the final part of your leave and maternity pay.
Ah, no, sorry, it changed in 2011, so long as you're entitled to maternity pay but have returned to work and stopped claiming it, your DH can apply for additional paternity leave, so long as it's after 20 weeks and taken in a single block. Can't see anything that says there can't be a gap.