Has anyone tried combining these before?
You blast your foe with positive energy. The positive energy damage from positive blast and its composites harms only undead and other creatures harmed by positive energy. It never heals creatures, even if they would be healed by positive energy, but it damages haunts and deals full damage to incorporeal undead.
You surround your body with energy or elemental matter from your kinetic abilities. You can use this form infusion as part of an attack action, a charge action, or a full-attack action to add damage to each of your natural attacks and unarmed strikes until the beginning of your next turn. Since kinetic fist is part of another action, using this wild talent doesn’t provoke any additional attack of opportunity. You deal an additional 1d6 points of damage per 3 dice of your kinetic blast’s damage (minimum 1d6), and this damage is of the same type as your kinetic blast’s damage. This extra damage ignores spell resistance and doesn’t apply any modifiers to your kinetic blast’s damage, such as your Constitution modifier.
So, you aren’t really doing the blast’s damage, just damage of the same type. So, does that additional positive energy damage from kinetic fist hurt living creatures or not?
It doesn’t have the same limitations because it ignores spell resistance. It’s questionable if it’s even a “blast”. It doesn’t deal blast damage, just damage based on how many dice your blast has.
Damage of a type that specified in the only place that references it 'harms only undead and other creatures harmed by positive energy'. It's not clear to me why using it via a particular form infusion would change this, when that form infusion doesn't explicitly mention changing it.