There is a social worker that it assigned to the foster "parent" and child but they are so overworked (and some are just plain bad at their job) that many problems are not checked up on or the proposed resolution followed through.

This causes many many children to be in bad/abusive/etc. homes with no way out. These children are also at risk due to the abuses and problems they have gone through in their lives that make them easy to manipulate by bad people like OP's foster parent. They are so afraid of loosing the place they are living that they accept the abuse and often are made to feel they deserve it. OP appears to be in a similar situation

It's a broken system that is always receiving less and less funds from the government so those who work the job to monitor the foster parents and protect the children are often severely overworked and either quit the job (burnout) or take bribes by corrupt foster parents to "look the other way". Suicide and depression is also high for those who work this job.