I don't know that your loaches act like they're being aggressive. To me, they act more curious and playful. I no longer have clown loaches, but from what I remember, they sometimes come to mid-water, and even top-water; they aren't always at the bottom of the tank. I have several Yoyo loaches now, and it isn't unusual for them to come to the top for food.
I think your tetras will be ok as far as loach aggression goes, but IMO
, add a few more so they feel a bit more comfortable. I think the amount of plants you have will be sufficient, especially after you increase the school size.
As far as your PH goes, 2 pts higher than recommended probably won't damage your fish, as long as you transitioned them to it slowly. However, someone else with more tetra experience and a wiser head may offer a different opinion on this.