How can I extract normalized read count values from DESeq2 results?
The normalized counts themselves can be accessed with counts(dds, normalized=T).

Now as to what the baseMean actually means, that will depend upon whether an "expanded model matrix" is in use or not. Given your previous question, we can see that geno_treat has a bunch of levels, which means that expanded models are not in use. In such cases, the baseMean should be the mean of the base factor in geno_treat.