The mandate was not a land transfer. The Mandate had no land to give. The Mandate was Jewish citizenship along with the other citizens.
Arrrggghhh. You get so much right and then lose it on the simplest, most basic principle because you don't happen to like it.
Let's take your first sentence and say I agree with you. The Mandate for Palestine was not a land transfer. Like all the other Mandates none of them were land transfers. Strictly speaking, "land transfer" is inappropriate terminology anyway. Land was never transferred from one sovereign to another (as were other territories transferred, or ceded, from Turkey to Greece, Italy, etc). The Mandate territories rather saw the dissolution of Turkish sovereignty and the creation of several entirely new sovereigns. The question, then, is how those new sovereigns came into being.
So. Let's walk through this. Turkey renounced the territory. This makes the territory terra nullius -- territory under the sovereignty of no State. The rights to create a State are invested in the two groups of peoples who make up the two ethnically distinct cultures in the territory, each with rights based on long-term residence or indigeneity in the territory. The persons responsible for protecting the rights of both peoples was the Allied Powers, and, eventually, the British for that particular Mandate. With me so far?
The Mandate for Palestine, which whether you like it or not, is a legal document, expressing the intent of the Allied Powers who were the ones responsible for putting into practice the Treaty of Lausanne, specifically the phrase in Article 16 which states:
the future of these territories and islands being settled or to be settled by the parties concerned.
Let's say we even agree that the parties concerned are NOT the Allied Powers, who are only the protectors of rights but have no rights themselves. Let's say we agree that the "parties concerned" are the two peoples residing in the territory, with rights to sovereignty. Still with me?
Okay. So how does a peoples with the rights to sovereignty actually create a brand new, never-before-seen sovereign State? We've been through this before. There are four criteria: they have a permanent population; a defined territory, they form a government, and they develop the capacity to enter into relations with other States. They often also, though (as you correctly point out) not necessary, become recognized by other States.
All of these things were achieved by Syria, Iraq, Lebanon, Jordan and Israel. And there isn't much room to argue with any of it, other than perhaps small matters of detail.
Here's where you go terribly wrong:
The Mandate was not to create a Jewish state.
No where is there a prohibition for the Jewish people which prevents them from forming a State. Whether from the Mandate documents itself or from other international law -- there is no prohibition on any peoples forming a State for self-determination. On the contrary, as you constantly remind us, that right to independence, territorial integrity and sovereignty is an INHERENT right of all peoples. You absolutely can not continue to remind us of that basic concept while simultaneously prohibiting the Jewish people from that right.