Hi Sam,
Sorry to hear of your troubles.
I have several ideas, hope they help:
1. you mentioned that now even rocking to sleep doesn't work... my dear, rocking should not be used for puting to sleep... one of the baby whisperers main points are to teach your child to fall asleep on their own with no prop. a prop is anything that the baby must use to fall asleep (rocking, breast, car ride, holding moms hand or even a pacifier or blanky can sometimes be a prop). I suggest you don't use any of these for putting to sleep.
2. regarding the number of naps, you mentioned that in October he will start daycare where there is 1 nap. that is ok since he will be over a year by then and at the age of 1 they usually drop to 1 long nap in the middle of the day (2-2.5 hours). now it seems odd to you beacause your baby seems soooo tired. you will see once you get back on track and once he is older that he will be just fine with 1 nap.
3. the sleep cycle is known: good sleep during the day means good sleep during the night and the opposite. so we really need to get you guys on track.
if you have the BW book, take a look at the chapter of PU/PD and read the part that is relevant for 11 months (by now your baby can sit or maybe stand so it is mostly just PD). you need to decide that you really are planning to do everything according to the book and then start. the BW always says: START AS YOU MEAN TO GO. if you keep on changing methods (rocking, shushing etc.) this mixes up your baby and he doesn't know what is expected. If you decide to set things straight with PU/PD then read about it, find a weekend where you can start since it will be hard with lots of screaming (your husband should probably do the first nights and naps if it is possible). if you stay with it (even if it takes an hour or more to put to sleep) it WILL get better with time. each nap will take less time to put to sleep.
The older the baby is, the harder it is to change habits but it is still possible.
4. you meniotned that the old schedule dinner is at 16:45 and bed time is 18:00. that is too early.... bed time should be around 19:00-19:30. Dinner should be at about 18:00 and then bath, book/song, bedtime (bottle/breast before bed if you have that).
16:45 is more of a snack time if required (fruit, peice of cheese, some cheerios)...
5. I suggest you take a look at the suggested number of nap times for an 11 month old (it may be 2, I don't recall). I know it seems odd but the point is that if he naps well during each nap, he won't need a 3rd one and will be able to go to sleep at about 19:00. in order to have the naps longer this is where PU/PD comes in to the picture. so check out the part about making naps longer.
Let me know if you have any specific questions.
Good luck!
Tammy