Not sure what you mean by "doesn't say God is in the midst of all things" because it says;
"The light which is in all things, which giveth life to all things, which is the law by which all things are governed, even the power of God who sitteth upon his throne, who is in the bosom of eternity, who is in the midst of all things."
I'm afraid I'm entering the realm of the mysteries or speculation.
1John 1
.... God is light, and in him is no darkness at all.
John 4
.... God is Spirit (not that this is the real intent of the passage)
and then in Rev 21, but first remember Jesus called his body his temple and our own bodies are called temples.
"...And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God. And God shall wipe away all tears from their eyes...."
and D&C 93
33 For man is spirit. The elements are eternal, and spirit and element, inseparably connected, receive a fulness of joy;
34 And when separated, man cannot receive a fulness of joy.
35 The elements are the tabernacle of God; .....
God has a tabernacle of element complete with hands to wipe away our tears.
So God is light+spirit+Tabernacle/body (that is your real trinity, some how it got all mixed up into this immaterial substance)
When the Bible speaks of the glory of God it says that no man can see his face or look upon him and live, without the Holy Spirit upon him. When John sees the risen Lord in Rev 1 it says "and his eyes were as a flame of fire" I take that to mean his countenance is so bright we can not stand in his presence.
Now this from D&C 88;
67 And if your eye be single to my glory, your whole bodies shall be filled with light, and there shall be no darkness in you; and that body which is filled with light comprehendeth all things.
68 Therefore, sanctify yourselves that your minds become single to God, and the days will come that you shall see him; for he will unveil his face unto you, and it shall be in his own time, and in his own way, and according to his own will.
So our resurrected bodies will become filled with light matching his own so that we can see his face.
Now here comes the way out there speculation part; my Mormons friends will roles their eyes at me.
I'll go back to E=mc2, Einstein came up with this formula in 1905 and means the denser the matter the more energy is stored within, and it has something to do, which beyond my finite mind, with the speed of light. A lump of coal has more stored light than a equal amount of oil which has more than a gas which has more than pure sun light.
However there is this; "Solid light is a hypothetical material, made of light in a solidified state. Theoretically, it is possible to make such a material, and there are claims this material was already made, including claims from MIT and Harvard." (Wiki )
So my theory is; while God is in the shape of a man he is solid light of some kind.
Do you see what I'm saying; to create, control and govern the universe it takes real power and not magical power, my solid God would have more real energy than your God of immaterial substance.
Now pack to D&C 88 written in 1832, there is a play on truth and light but I'm interested in the real physical light.
7...This is the light of Christ. As also he is in the sun, and the light of the sun, and the power thereof by which it was made......
12 Which light proceedeth forth from the presence of God to fill the immensity of space—
13 The light which is in all things, which giveth life to all things, which is the law by which all things are governed, even the power of God who sitteth upon his throne, who is in the bosom of eternity, who is in the midst of all things.
This revelation is address the real power of God and is really beyond any kind of knowledge Joseph Smith could of had.