Jason your practice place is beautiful but I hope fish don' t disturb your concentration too much
I see two same areas where you can improve your casting where I am working. First is doing slower initial line lift. When done slower it comes more consistent and then the back cast comes more consistent. When the line head is long at first we need to free as much line as possible but not lift rod too high. About 45 decrees is fine. Next is challenging part "the Dip" and it is essential because long line require either inclined back cast plane or a level plane which has an upward lift "flick and stop" in the end and without Dip in between there is no room to do it.
One way to do the dip controlled way is curling the top arm bicep which makes rod tip dip. This is what I practice now because it seems to improve my consistency. Then I try to continue back cast using just body rotation keeping arms locked again to improve consistency and then finish the back cast using bottom hand push and surprice
it seems to improve consistency too. However I am not athletically skilled and for me it is challenging because it does not go in perfect sequence: lift, curl, twist, push but those overlap slightly.
To improve my back cast consistency which starts when I lift the line I watch the line where it is about one feet above the water and at first this point "goes out" and slows down when rod arrives 45 decrees. Then when I begin the back cast curling the bicep the line tightens and more line comes out of water and to adjust the rod tip dip and beginning of body twist I try to keep this one feet height point "fixed there". Even more line begins to lift out of water and approach the leader but same time rod tip comes down and this makes the line straighter and line ancle lower.
Then when line frees out of water as low force as possible and as straight as possible there does not come too much line waves and it improves the following D-loop. Also when there is less bend in rod during the line lift it improves the consistency of the back cast to D-loop. Rod has three ways to transmit casting energy to the line and using rod as a lever and as a momentum is more consistent than using rod as a spring. Rod should not straighten in the middle of the back because it makes D-loop form more to the side which it easily does if too much bent rod "casts it" when line forcefully jumps out of water.
When D-loop is a line loop the back cast which is a cast should accelerate smoothly and end to an upward trajectory and stop abruptly and line loop comes narrow and D-loop improves. When Spey casting T&G we intentionally stop line loop straightening about half way setting the anchor. When SA casting we do it in reverse order.
Then comes forward cast and I can't write any tips to time it right other than practice.
I am prone to a casting fault Creep which is unintentional moving of rod forward when the D-loop (or line loop when OH casting) forms and Creep is bad when it shortens actual casting stroke. Creep usually lifts rod more upright as well which then together with shorter casting stroke bends rod a lot and when rod bends its span shortens and rod tip dips and it sends a wave to the fly line which is called a Tailing Loop.
TL can be so bad that it can cause line loop collision towards the end of the line loop straightening. However when Spey casting the water anchor placing often cause the fly leg of the line loop run further side than the rod leg of the line loop and collisions are not too common but because a TL is bad we should avoid it.
To avoid Creep I try to Drift which is intentional move of rod handle back and up and rod tip back and down when the D-loop forms. This lengthens the following forward casting stroke and makes it possible to produce more power. Drift also moves rod tip down and keeps line straighter when gravity cause the line to drop. Also when rod angle approach the line angle it does not bend too easy in the beginning of the casting stroke and TL lessens. There are much better Drift articles and videos worth reading and watching in internet for OH casting but it is the same for Spey casting.