The screenshots below show the maximum range for Personal Space that still grants a bonus.

Those are my test results for damage per rank of Personal Space:

- Base damage: 1176
- 1/3 PS: 1379 - +17,3%
- 2/3 PS: 1582 - +34,5%
- 3/3 PS: 1785 - +51,8%

So, yeah, it is, in fact, 18% per rank instead of the 12% stated on the card. Keep in mind that Personal Space is multiplicative. The more gun and elemental damage bonuses you stack on top of it the more potent each point in PS becomes.

It also seems to use a linear function in order to calculate the bonus based on the distance to a target. At 50% of the range shown in the screenshots above it should give 50% of the skill’s bonus damage.