How do strongholds generate in pre 1.9 I Know that theres only 3 per world but how far are they from the center of the world

random

there are 2 close strongholds and one far one, which are around 900-1100 and 1200-1400 blocks respectively

of course, this is just the average. there are hardly ever any strongholds farther than this, but there is a high chance of a closer stronghold than 1k blocks away

In pre 1.9 strongholds generate 640-1152 blocks away from (7,84) (this is because of biome snapping). There are only three and they are 120 degrees from each other. All random distances.

bedrock moment