Structure-wise, it is well balanced on the amount of material on each of your points. The intro could be more explicit in stating the overall theme the text is driving home.
Sylistic point, I think calling Paul a "killjoy" could be misunderstood. Though I know you intend to be ironic, it should be followed by a repudiation of that label, that in truth, preaching/Word is the ONLY SOURCE OF JOY that can be found in this world. It isn't in the whizbang methodologies of today, as that supposed joy is fleeting. As the disciples said to Jesus, "where can we go, Lord, you have the words of life"!
Also, generally speaking, the gospel message itself and Christ's cross could be more expanded upon.
On the conclusion, I think the rhetorical questions are fine. But I'm not sure I'd want to end the sermon with those questions hanging. You may consider answering them forcefully with some indicatives, calling the congregation to prepare their hearts, calling on all to trust in the Word and the Christ of the Word, their efficacy, to repent for being shallow, stony, to find true joy in the deep rooted soil that Christ has provided.........etc...............
Just some observations. Overall, good job.