Whatever guilt Remus was feeling about pulling dirty tricks to win, he pushed aside. There was no place for guilt on the field of combat and this was an anything goes match. The guilt would be dealt with later, when he had the luxury to feel it.
Right then, he was entirely focused on his prey. Once Harry's back hit the ground, Remus locked his elbow, rendering the flailing of Harry's free arm ineffectual.
He didn't care about Harry's wand. Once the petrification spell failed, he tightened his grip on Harry's wand hand and pushed it toward the ground, looking to pin it there where he couldn't aim the wand at Remus. That was hampered however, by Harry's struggles. The hand holding Harry's wand hand didn't have the advantage of leverage the hand holding his throat did.
In the grappling that ensued, he could see the sparks of a spell flicker at the end of the wand. But, whatever the spell was, it thankfully missed.
Remus was breathing hard from the exertion -- not the exertion of grappling for control of Harry's wand hand, but the exertion of controlling himself. There were instincts in battle and then there was Battle Instinct. Just then, the second was dangerously close to the surface and Remus needed to concentrate not to put further pressure on either throat or hand and cause serious injury.
"Yield, Harry." His voice was harsh with command, not willing to show weakness in battle. But in his head he was pleading with his friend to do it.