Really sorry to read your LO was so poorly
It always seems to me that routines take a good while to get back on track after illness, especially with young babies.
It could also seem like things were going well because your LO was in the new born sleepy phase - which can seem like all they do is sleep and in terms of routine might even seem easier than when they come out of it - and then came out of it around the same time he became ill.
Looks like you are coping pretty well with 3 children to care for - and really all you can do is fit LOs naps into the family routine which looks like you are doing. Your DD3 is still very young and many people wouldn't be experiencing an ideal routine at this age, not yet, even without the commitments of the school run to work around.
Things you might try:
- waking LO up earlier in the morning so that you can fit a 1hr 15 A time before getting into the car for the school run. So 7.30 WU and 8.45 nap in car seat (personally I wouldn't want to wake baby in the morning but it can help set up a more workable routine for you)
- allow LO to sleep longer in the car seat instead of transferring (car seats are not ideal sleeping places but often this can't be avoided due to there being other children to care for)
- if the first nap remains short, a CN, to reduce the A time following it and put LO down for the 2nd nap earlier, say 10.30am whilst this is only 1hr A time and for age guidance is more like 1hr 15min it comes after a short nap rather than a long one. You might find with some help he can lengthen this second nap and sleep 10.30 - 11.45 when you have to transfer to the car seat for the school run. It's not an ideal length nap time but it's better than only 45min
- with some jiggling around with times you could, if you chose, aim for
an earlier WU (7am)
S a CN before the school run (8 - 8.45am)
A 1hr 15
S a longer 2nd nap 10 - 11.30 (up in time for school run)
A 1hr 15
S 12.45 - 2.15/2.45
As A times naturally increase with age you could then drop the morning CN and go directly to the longer nap at home after school - sounds great in writing, perhaps not so easy in real life.