On your point about ratings being stagnant. If you look at viewership trends for most TV shows they tend to lose viewers the longer they are on the air. An upward trend is a positive no matter what for Spike TV. It's not necessarily what TNA wants, true. Spike gets two hours of prime time every week that normally does a 1 or higher that is aimed at their key demo. If the ratings are on an upward trend it can only be good.
Did Spike sink a lot of money signing the big names you listed? Yes. But if TNA keeps getting 1s and continues their upward trend (I'm ignoring the Monday Night fiasco to better illustrate my point.)
Spike TV is a niche cable network whose overall viewership has been dropping like a rock. Should TNA be doing much better? Perhaps. Could TNA be doing much better? Most definitely. While I agree with your premise that they should spend more money on advertising, let's not act like TNA is a sinking ship.
And on your point about TNA's drug policy I can only say that the absence of evidence is not evidence of absence. Especially when it comes to the inner workings and policy of a privately owned company. Information related to drug policy penalties and failed tests hurt both the company and it's workers, I don't think it's too far out of the question to think that TNA doesn't compromise storylines for drug policy violations. For example perhaps Samoa Joe's unexplained kidnapping and disappearance was really a drug policy violation. We don't know for sure.