My solicitor said the judge won't give the sole custody to one side parent unless the other parent is metally ill, drugs problems or voilent. This is nothing deal with the maintenance unfortunately. Coz both parents have the same right to make decision for the child. Regarding to the tax allowance and maintenance for the child, it really depense on how much he earn and how much you earn.
For the 'Care and control', it is true the law is favour to the mother most of time, in my case, I am full time working, but I can proof I am the primary career to my children even I have a helper, thanks to my very good solicitor, whose helping me fight and get the 'Care and Control", and quite a reasonable maintenance for my children and myself.
I think you really need to find a good and reliable solicitor, if you get a wrong one it can really ruin your divorce case.