@Phoenix_Rising
Firstly - really awesome work there. The tension is actually pretty good, your tension has improved greatly from the previous two pieces, so keep doing what you're doing. You have quite good stitch definition. Good 1st chain and first row and the work is quite consistently tensioned. All in all, excellent progression here.
Have you thought about a simple item you'd like to make when you feel more comfortable? perhaps still a square or rectangle, but so you have an actual finished item (made using the same stitches you are using for this piece) to smile at. (I usually recommend a wash cloth made from a cotton or cotton acrylic blend.)
PR - How the heck did I end up with MORE stitches per row as I went along???
When I embiggen (I do love that word too @CheerBear it amuses me) the image I can't clearly see the exact number of chains in the beginning row -it looks like 12, but could be 11 or 13.
It appears the very first chain made has been missed for the 1st row at the tail end. (see how it hangs down instead of being held straight if there were a stitch into it? ON the other hand, that might be a loose slip knot and if it is, all it needs is a bit of tightening and it's okay)
On the 2nd row, the end stitch (opposite the side with the yarn tail) has been missed. I think some of the end stitches are being missed and sometimes the turning chain is being worked into.
The discrepancy seems to be occuring when the turning chain tension is a bit loose to sorta see properly, if that makes sense. But in truth, you're doing well.
Are you finding the plain coloured yarn easier to work with? or do you still prefer the multi coloured yarn? For me it's easy to see how good your tension and stitch definition is in the middle of this piece with it being plain coloured.
I wonder what your feelings were (not that I'm asking you to explain) as you were doing the last 5 or 6 rows, or if your hands were getting tired. They are the only rows that deviate from your good tension and consistent stitch definition. (hopefully that makes sense too 
)
Remember, if you see something that doesnt' look quite right, you can undo it back to where you can see it being as it should be too. (I'm sure you've read where I'm just constantly undoing cos my tension and stitch count is so off 
)
I'm still struggling with the turning bit,
Okay, the turning chain - is there anything in particular you can describe that is the reason for the struggle here? I might not address what is bothering you otherwise.
Tips: try to always make that turning chain at the same 'end' of your work.
Sometimes people do it as the final stitch BEFORE turning the work, and some do it as the first stitch AFTER turning the work.
It's important that it is consistent throughout the work, for the appearance of the project, and for the way the stitches sit, and so you can recognise that pesky chain and not work into it.
Also, try not to let it get too loose, sometimes they have a mind of their own and want to wave at everyone, turning chains support the rest of the work rather than be the visible star of the work. 
Have you been trying with stitch markers so you know where the end is? did it help or hinder?
and I am also struggling to find the best way to hold the yarn. I still can't figure out how to hold it so that I can keep a consistent tension and it moves properly through my fingers.
Yeah, understood. Like CheerBear has said, this one is a tough one for all of us who crochet. I currently use the method I showed in the images, but it can change too if my hand is particularly painful.
Will post this now and do a follow on post with some images 
Also, could you maybe tell me (using very small words) exactly what I should be looking for in a ball of yarn? My hook is 4.25mm (G/6). I went to spotlight today and after looking at a bazillion balls of yarn, I realised I really don't know what I'm looking at. 
