Get him in a stack as an auxiliary general(3 years at least), devastating tiles, commanding or generally just not ending your turn in a settlement(especially during winter)/being active as a character. Some characters are languorous, which predisposes you to Weak Kingetos. Likewise, Vigorous characters are predisposed to success.
2. You must be doing something wrong. Every single time I win a battle during the training level(assuming I'm commanding), I get the Kingetos success level. My guess is you didn't trigger the training level, and didn't read the Game mechanics info for the trait(the description says everything, basically). You need to exhaust most of your movement points, or end your turn InEnemyLands, and then the training level will kick in. You only have till age 30 till you auto-fail this trait. Not to mention, you can only go from Kingetos to Epas if you're under 30.
My guess is that you haven't gotten the training level when you didn't trigger the training level before fighting the battle. In the future I'll upload a trigger fix allowing Youths who win a battle pre-training to succeed the training before it even begins.