I don't believe Survival mode has the character combos you are talking about. I believe it is just more about setting up the board and always look a few moves ahead of what you are currently working for. I don't remember what level I can usually get to because I like to play MD3 in Japanese and I cannot read Japanese
I find once you get to the numbered blocks it allows me to chain a lot easier and nearly clear the screen. Those always give me a nice reprieve.
Have you play faster and with no hesitation. Don't waste time shuffling things around too long, just go for the quick clear while also paying attention to combos as much and fast as you can. Takes a lot of practice, but game rules so much. I just wish more people knew or got into this game so I would have more people to play against that had skills.