Firstly, Yeshua was not the Passover Lamb in the context of a "sacrifice". Please check out our article - http://www.therefinersfire.org/passover_lamb.htm. Secondly, there is no Torah command against martyring one's self! Thirdly, the Hebrew seh can mean either sheep or goat.
Yeshua's sacrifice is utterly unique and cannot be compartmented or compared with any other offering or sacrifice in the Torah. Also, if you read Zecheriah 12:10 and understood the words et asher dakaru you would understand why Y'shua is a Yachid instead of Echad - only begotten son - which means never before, never again, ONLY with Him!
Offerings "qurbana" and sacrifices "dabekha" are two different entities. Although there are certain aspects to Mashiyach's death that are utterly unique to him (Zechariah 12:10, etc.), his death nevertheless echoes aspects of offerings and sacrifices that came before. The qurbana is the human life (nefesh) that Y'shua voluntarily offers up on the stake. The result of that offering is his blood put out on the "altar"; hence dabekha.
However, this is certainly not, as some critics suggest, "human sacrifice." Rather, this indicates Y'shua's status as Mashiyach ben Yoseph. Per strict accordance with Isaiah 53 and Genesis 22:8, Mashiyach ben Yoseph was required to suffer and die. After his death, the offering of himself became a sacrifice that was taken up, and he was resurrected three days later. Many of YHWH's prophets also suffered and were martyred at the hands of those who fought against the Malchut Elohim. In the case of Mashiyach, his shed blood is counted as the acceptable offering, the Lamb of YHWH, which is most Set Apart unto YHWH.