While using Distruptive Strike, can you expend more than 1 Force Point to add more than 1 Failure to the opponent's next combat check?

Yes.

GODS I want to play a Shien Expert...

#alwaysthegmneverthepc

#coughnemesistime!

While using Distruptive Strike, can you expend more than 1 Force Point to add more than 1 Failure to the opponent's next combat check?

Far as I know, the only place where it gets called out that you can't spend multiple Force points on an effect unless it says otherwise is with Force powers.

So with any of the talents that say 'spend Force point to get this effect,' you can spend as many viable Force points as you generate.

So yes, with Disruptive Strike and a lot of Force points, you could pretty much ensure that you're opponent has to roll a mountain of successes in order to hit you in the first place, leading to better odds of a failed combat check with some Threat left over.