Revelation 10:7 But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.
The phrase “when he shall begin to sound”, when looked at in the Greek, should read “when he shall be about to sound.” Most commentaries say the mystery is finished at the same time the trumpet is sounded. Some of the Premill commentaries place the beginning of the millennium at this point which coincides with the mystery being finished and Revelation 11:15.
I’m no rocket scientist but it looks like you have the seventh trumpet sounding at the same time as the fifth trumpet. After the sixth angel sounds and unleashes his plague men still don’t repent according to Revelation 9:20-21.
If your chart is correct then apparently the mystery of God that is finished has no effect on the unsaved because they still don’t repent. What is the mystery of God that is finished when the seventh angel sounds?
Rev 10:7 is definitely not the start of the 7th Trumpet. It is directly occurring after Rev 9:13-21. After the 1/3 kill-off of humanity, then the covenant of peace is confirmed. Trumpets 1-5 = Daniel 9:26
The mystery of God is that the 'mighty angel' in Rev 10:1 is the prince of Tyre, the 'guardian cherub' of Ezekiel 28:14, and is the 'antichrist', the Daniel 7 Little Horn of the 4th Beast.
This 'mighty angel' breaks the covenant of Dan 9:27 at the 7th Trumpet - that is when the 'mystery' is revealed: surprise! there is another abomination to tempt the unfaithful who did not repent at Revelation 9:20-21.
Roughly speaking it means the 'mystery' is that there are actually 2 abominations: 1 that kicks it off going roughly from the 4th or 6th Seal (we know this because the potential kill-off of 1/4 of the world in the 4th Seal would be the equivalent of the 1/3 kill off in the 6th Trumpet:
8 billion - 1/4 = 6 billion. 2 billion killed.
6 billion - 1/3 = 4 billion. 2 billion killed.
Same amount of 'great tribulation' (2 billion dead.)
Alternately, if people are thinking it is the literal end of the world like in the 6th Seal, then this would be the start of the 'great tribulation' (when the abomination begins).
Bottom line, after the 'great tribulation' is over - then the false christ arrives: read Matt 24:15-24 again.
Note: there is probably 1 month between the abomination and the start of Feast of Tabernacles (the start of the Trumpets).