META-INF/container.xml must point to the correct location of the OPF file (which can have any name and be located anywhere). The location specified in container.xml is relative to the root directory of the epub (i.e., not to the location of container.xml itself, which must me META-INF)
The OPF file must have a manifest of the other files in the epub, and the locations there must be relative to where the OPF is located. So, if everything is inside OEBPS, then the "hrefs" in the OPF are just filenames. But if the OPF is in the root directory and all text files are in OEBPS/Text, the "hrefs" must contain OEPBS/Text/...