[y not]

Your point 2: Precisely! It seems you did not get me right. By ‘there is no unchanging entity’ I meant there is indeed an entity,and one that persists all through sansara and Nibbana taken as one unbroken stream of existence – but it is changing all the time, as yet, but will no longer do so on reaching Nibbana.
As to your point 1: I have given a lot of thought to this too. Now if Nibbana exists, it must exist outside the 31 realms, necessarily implying that the ‘Sphere of Space’, as it were, is not infinite, for the realm of Nibbana would lie outside of it, and Infinity means that which comprises EVERYTHING, with no limit to it. Or otherwise, Infinity would comprise Nibbana as the outermost ‘shell’ enveloping the sphere of the 31 realms, much like the higher realms of any inhabited planet envelop those below them. A more difficult point to consider is your notion of’….with individuals who all attainded Nibbana’. It is said by some that individuality is lost on attainment of Nibbana, because it was individuality, the seperateness, the exclusivity of personalized existence which had given rise to the ego in the first place, and ego divides the one from the many…this is for the most part the fruit of Mahayanist literature, to be sure, but the point is: If all these Arahants, from beginingless time, attained Nibbana, then their number would be infinite, and if all had shed their individuality, their charachter, so to speak, there would be no distinction between one and another, they would the be more like inert, becuase devoid of any marked charachteristics, clones. No…individuality, the being as distict from any other being, must perist even into Nibbana.
As to why their number must be infinte, even though an Arahant is difficult to come by, say one in a million years on this one planet:
imagine a line of marbles,say,of infinite lenght. The number of marbles would be infinite. Now I colour one very 10 marbles black, or one every
thousnad, or every million, or every highest number you can conceive of, and see that the number of all these uncoloured marrbles is not greater than the black ones – just because the line is infinite in lenght, both set of marbles are equal in number. Both are infinite. In mathametical parlance we could say that a fraction of infinity is equal to infinity itself.And just because of that, the number of those who have attained Arahantship, though it be the rarest of attainments indeed,must be infinite.