Re: Just starting out, advice appreciated.
It sounds like mostly what you need is practice, although it also sounds like you're beginning to develop your technique.
Quick note: I know several good tennis players in my area who didn't begin playing until their 20s or 30s. It's never too late to learn.
Advice: You might try going into a local tennis/sports equipment store and testing out some "demo" rackets. Usually, they'll loan these to you with a deposit or minor form of collateral (current racket, etc.). A new racket might help with your slice or backhand. I switched rackets once and was finally able to hit a flat backhand.
There are probably better quality players that can provide more tips for you. But I'd say, join a local tennis club - even if it's a rec league. The more you play, the more people you play with and against, the more you'll get to practice your game.