That's against the rules of Google's and Apple's Terms of Service.
Trading reviews and "returning the favor" of it could potentially get you banned from the App Stores entirely.
Apple App Store Guidelines
3.10 - Developers who attempt to manipulate or cheat the user reviews or chart ranking in the App Store with fake or paid reviews, or any other inappropriate methods will be removed from the iOS Developer Program.
Google Play Developer Program Policies
Developers must not attempt to change the placement of any Product in the Store, or manipulate any product ratings or reviews by unauthorized means such as fraudulent installs, paid or fake reviews or ratings, or by offering incentives to rate products.
There's alot of shady reviewing going on in the app stores, and Apple and Google know they has problems with it, and can occasionally take action against people it catches.
You are basically paying for a review, you're just not paying in cash ("I'll return the favor [with a review of your game]"). Further, you're only asking for positive reviews (Yes, you did imply that in your post, and yes that is what you are asking for, even though you may not want to think that's what you're asking for) - "if you like what I made" (i.e. 'if you have a positive opinion of what I made').
Also, you are asking the reviewer to manipulate search results with keywords ("I would appreciate it if you would use some keywords like...").
If you want to cheat the system,or just "fudge" it (i.e. cheat) a little, you should be aware that the gatekeepers might catch you.
As a customer, when you read a review, wouldn't you want to know that that positive review was written by another developer who got his app reviewed in exchange? I certainly would.
As a customer, now I doubt every one of the reviews for your game (I notice there are 80 5-star reviews), and that doubt reflects on your integrity as a developer. "Can I trust a developer who lies to me to get me to install his game?"
I think, as a craftsman, professional integrity and respect towards one's customers is very important. Making a living is also important, but the two don't have to be at odds.
Unfortunately, you're right that the market is very very hard to break into, because it's way over-crowded and because there is alot of shady developers doing shady promotion to cheat the system in their favor. 
But the solution to the problem isn't to become part of the problem.
Best of luck releasing your app - hopefully it'll gain enough legitimate reviews and legitimate customers to be worth the hard work that it looks like you've put into it.
[Edit:] That was a bit overly preachy, but I did want to get two things across: A) If you're not already aware, it is against the app store rules and you're running a risk. B) If your customers find out you lied to them, they will despise you for it, which is worse than them not having heard of you in the first place.
