1: I assume you mean high ground and the 'standing behind someone gives you advantage' backstab thats in the game. High ground shouldnt give advantage imo but either nothing (you are already negating most types of cover almost completly) or just a flat to hit buff. Granting both advantage and the enemy disadvantageg is way to overboard. Now, the backstab I dont have that many problems with tbh. In dnd enemies that you cant see that attack you gain advantage. Its only an issue when you use facings though because everyone in combat that isent blind is assumed to know where you are but facings have a more nuances approach. That said if they include the facings system, include all of it. If you cant alter your facing with a reaction its more of a downside then an upside. Most of the times (most likely anyway) we will also be outnumbered as a group of adventurers. It would effect the players more. But overall I agree thats its way to easy to get advantage at the moment.

2: You mean that all classes get cunning actions for free? Yea, hate that. Agree.

3: Agree.