Peveril isn't pruned normally - they are big plants, that's their nature (5-7m). If you have to prune to control their size do it after flowering.
No, that causes complete collapse. It's more likely to be uneven watering if they're in pots.
Well, part of the argument is that seeds only have a finite life, so if you suppress them long enough they'll be dead before they can get the chance to germinate.
If any hole that you dig fills with water it suggests that your garden is very low. If that is the case then you can't really condition the soil to help matters, but need to raise it.
There could be all sorts of reasons. A few brown leaves are quite normal at this time of year, but a large amount is not. Did it dry out early in the year? Is it in a small pot that was caught by a hard frost?
Camellias need an acid soil - do you know if your soil is acid?
JI should have been fine. I would leave it where it is and make sure that it doesn't get too wet again. Hopefully, it will put out fresh shoots in time.
Simply pull or dig them up.
It depends - if you have pigeons you may well find that they will cause severe damage to anything leafy.
It may be over-wet - is it in a particularly soggy piece of ground?