I am so sorry to see this RR.
If the docetaxel didn't have any great effect on the cancer last time, are they suggesting cabazitaxel this time round? They don't usually offer a repeat of docetaxel if it didn't work very well anyway.
I can't think of any other treatments now apart from a different chemo like cabaz. Probably the most important thing right now is to get on top of these symptoms so that he can be as comfortable as possible. It is often the case that the local hospice or palliative care team are the best at sorting out pain and other symptoms - far more experienced than oncologists or GPs. Has he been referred to hospice care / palliative care / Macmillan? If not, ask for a referral as these services will support you, him and your combined children. Also, is he in receipt of PIP? If not, ask the hospice team to help you apply for this - there is a fast track application if he is thought to have less than 6 months although many medics will sign the forms if they believe the patient may have less than 12 months and / or active treatment has been stopped. Continuing with the Prostap doesn't count as active treatment at this stage. It is important that he applies for whatever financial help is available, it is not means-tested and he is entitled to it - it can be used to help pay for things that will make his life easier (practical and emotional), keep him mobile and / or to help pay for domiciliary care when the time comes so that you can concentrate on being his love rather than his carer and / or just so that you can get some sleep.