Time -1 means he spawn right at the start of the raid.
10% is quite smol, it can be once in 10 raids, or you can be unlucky and not see one in 50, that's how probability works.
Although be sure you have `Bosses Enabled`, or you end up with 0% chance of any boss.
Alternatively you can get SVM self promo(1.5.3 for AKI 3.1.1 IIRC) and check `increased boss chances`, which cranks them up to 100%.
Wrong, 3.1.1 is 19078, while 3.2.3 is 19428
That will require new client files
Maximum you can update is to 3.2.1.(which is a good move, because you'll be able to use most mods that is built between 3.2.0 and 3.2.3 versions, unlikely they'll have compat errors.
Speaking of raiders, there is issue on 3.2.3 related to them that is being worked on already.