impossible to boot ep3c25 from epcs16 - reset_vector problem ?

Yes Altera developed this functionnality, it is called system console (http://www.altera.com/literature/hb/qts/qts_qii53028.pdf) tools. There are commands to read and write specific addresses, and you should be able to use them to test the memory.

For the memory test program, you can try and reduce its size by selecting the small drivers option, removing c++ compatibility (I'm not sure this one will reduce the memory footprint though) and changing the compiler optimization option to "optimize for size".