Hello Pietro di Castri:
The memory map in Table 4-1 only represents an overview of the memory spaces that the MCU architecture could eventually handle depending on the specific device (part number). The actual RAM sizes and addresses are given in Chapter 3.5.3.1 SRAM sizes:

About the vectors, the 0x400 space for vectors is the standard reserved size for Kinetis devices; the actual space used depends on the number of vectors as you implied. For your case with K02 the space required is 90 x 4 bytes = 360 = 0x168. There is an unused gap but it is not possible to place code from there because it would overlap with the Kinetis Flash Configuration Field space (from 0x0400 to 0x040F).
Regards!,
Jorge Gonzalez
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