Are male humans ever used as surrogate “mothers” for implantation of human clones or human-alien hybrid embryos, perhaps via intraperitoneal implantation for a time sufficient to allow enough growth they can be harvested and maintained in vitro, thereafter?

This is technically feasible to do and is sometimes done with female abductees but is not done in males as a matter of routine. The extraterrestrials are honoring the system, at least up to a point, in using female surrogates to raise their hybrids, whether naturally or unnaturally, as the case may be. So this is not a consideration in terms of their strategies and exploitations of human beings. It is only human females who are used in the breeding program, other than using males as sperm donors in some cases.