Regarding your question about Lord Jesus Christ, we accept him as saktyavesa avatara. Lord Buddha is in the same category also. Lord Buddha is mentioned specifically in Srimad-Bhagavatam as incarnation of Godhead, and yet Vaisnavas do not accept his philosophy, which is classified as atheism. Similarly, even if we accept Lord Jesus Christ as saktyavesa avatara., it doesn't mean that we have to accept his philosophy. But we have all respects for him without fail.
Letter to Hamsaduta, 2 November, 1969