I'm going to have to give you a C- and only because this stuff can be pretty confusing and we have to grade on a curve.
The verse that pulled you out is 2 Thes 2:3. But if we read verse 2 Thes 2:2 we can see that the man of sin will be revealed before the day of Christ.
2 Thes 2
2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
So the people were concerned that they were in the Day of the Lord but were told........no.....before that happens the man of sin will be revealed.
Secondly the verses of 1 Cor 15 are not talking about a pre tribulation rapture, they are talking about the main harvest which we can see at the end of Rev 14.
Thirdly you should read Matt 24 again. It has some interesting verses.
Matt 24
29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
30 And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
31 And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.
32 Now learn a parable of the fig tree; When his branch is yet tender, and putteth forth leaves, ye know that summer is nigh:
33 So likewise ye, when ye shall see all these things, know that it is near, even at the doors.
34 Verily I say unto you, This generation shall not pass, till all these things be fulfilled.
35 Heaven and earth shall pass away, but my words shall not pass away.
36 But of that day and hour knoweth no man, no, not the angels of heaven, but my Father only.
37 But as the days of Noah were, so shall also the coming of the Son of man be.
38 For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage, until the day that Noe entered into the ark,
39 And knew not until the flood came, and took them all away; so shall also the coming of the Son of man be.
40 Then shall two be in the field; the one shall be taken, and the other left.
41 Two women shall be grinding at the mill; the one shall be taken, and the other left.
42 Watch therefore: for ye know not what hour your Lord doth come.
43 But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up.
44 Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh.
So after telling you all the things that are going to happen.......wars, famine, pestilence etc. and then immediately after that tribulation He is coming.......YOU SHOULD KNOW WHEN HE IS COMING. And yet he says for in such an hour as you think not the son of man cometh.
He's telling you be ready because Noah goes into the Ark 7 days before the flood. The times of the Gentiles get fulfilled. Then comes the 70th week of Daniel.....7 days when God deals with Israel.
Fourthly if you really studied when the teaching of the pre trib rapture began, you would find there is plenty of documented evidence that proves that it was around long before Darby and Scofield etc. This can be easily proven if you do a little research.
You might want to rethink everything and be ready before the doors to the Ark are closed. (7 days before the flood for the Gentiles)