Is it permissible for a woman to refuse to serve her husband and breastfeed her children and to demand wages for that in Islam, as has been reported from some jurists?

The correct view is that serving the husband and breastfeeding the child are duties upon the wife, due to the prevailing custom. Absolute contracts, such as the marriage contract, are interpreted according to what people customarily agree upon. An exception to this is if the wife is of a privileged background and it is her custom not to serve her husband or breastfeed her child, then she is not obligated to do so. The wife is not entitled to a wage for breastfeeding her child while the marriage subsists, because Allah Almighty has only obligated for her clothing and maintenance according to what is customary. These matters are issues of ijtihad (independent reasoning), and a mujtahid (one who performs ijtihad) is rewarded even if he errs, provided that he is qualified for ijtihad and his intention is to please Allah.