1 -Not sure what the limitation is with the bram and the net vanilla, but I now you can minimize the cache in microblaze to save bram if needed.
2- That module is only 1M that sounds really tight, but for a very basic setup may work. You need to configure it over the 0x80000000 space.
3- Here in US I think the MAC module cost about $1200 or so, but the EDK has a free demo version that will run for several hours at 10Mb/s or a few hours at 100Mb/s, then you need to reset.
By the way, did somebody tried the MAC lite, is there a compatible driver?. Iam not sure if that one is free (sounds like it)
I hope this help,