You have mistakenly associated Rev. 6.12 with the end of the Tribulation in Matt. 24.29. Notice Rev. 6.12 is a solar and lunar eclipse and a rare one at that. Matt. 24.29 is not a solar eclipse or lunar eclipse but simply darkness. Matt. 24.29 is associated with Rev. 11.19. Rev. 7 to 11 (chapter 11 being the end) are the major points of the 7 year Tribulation. Rev. 12 to 19 are the details.
Seals 1 to 4 are the past 20 centuries (the 1st Seal recounts the cross), and Seals 5 to 6, general and vague in scope, are just before the Tribulation. Also Matt. 24.31 is the Jews being brought back to Israel to reclaim the nation after they were dispersed during the Tribulation. During the Great Trib the 3rd Temple will not be destroyed. That's why Rev. 11.2 says not to measure the court outside the Temple because it will be overrun. So Matt. 24.31 is not the rapture.
Rev. 6.12 occurred already 2010-15 to point to the nearness of the Lord's return. The 2nd most deaths of any earthquake in human history was Haiti killing 320,000 people. The solar eclipse was the long H3 Hybrid Nov. 3, 2013, the 4th since Christ. Extremely rare! And the Lunar Tetrad on feast days was the 8th since Christ 2014/15, the 6th feast Tetrad, coinciding with when Israel became a nation and the 7th was when Israel took over Jerusalem. Put together this has never happened before in human history.
Go now to Rev. 11.19 which says "And the temple of God was opened in heaven, and there was seen in his temple the ark of his testament: and there were lightnings, and voices, and thunderings, and an earthquake, and great hail." This occurs at the end of the Tribulation not the beginning. It has no solar or lunar eclipse.
Joel 2.31 and Rev. 6.12 go together. They don't go together with Matt. 24.30-31 nor Rev. 11.19.
The first rapture is according to readiness. These are clear conditional statements in Matt. 24.40-41, Luke 21.36, Rev. 3.10 to be taken up "before the throne" (Rev. 7.9) in 3rd heaven before the 1st trumpet of the Tribulation (8.7). Not all believers are watchful, prayerful and keep the word of His patience to escape the hour of trial all these things that shall come to pass at the end of this age.
Partial rapture was stated by T. Austin Sparks as an advanced party and harbinger like we observe in every sphere of life. Watchman Nee also taught partial rapture. Watchman Nee had the highest IQ of any Christian in church history, had a collection of over 2000 Christian books and was martyred the last 20 years of his life in prison.
The saints who were not first taken, but left (1 Thess. 4.14-18) to be taken up at the last trumpet (not the 1st trumpet) still have time to overcome when they are in the Tribulation. If martyred they will go to sleep and wake up 3.5 days later. Only overcomer believers, not all believers, return with Christ to reign over the nations with a rod of iron (Rev. 2.26,27; 20.4-6) for 1000 years, before the New City and New Earth commence.
Praise the Lord!