One thing you need to remember with glucometers. They are allowed to read within 20% plus or minus and still be considered to be accurate enough. So even testing the exact same blood drop, can give you different results.
So taking your 3 examples, here are the ranges.
207 + 20% = 248 207 - 20% = 165
171 + 20% = 205 171 - 20% = 136
223 + 20% = 267 223 - 20% = 178
What looks like numbers all over the place, what your called "roller coaster numbers", are really numbers all pretty much within the same range. You'll never get the precision you seem to be expecting, no matter what glucometer you use for testing.
It's why we have the spreadsheet with the color coding. So people can see the ranges with the colors and see patterns instead of focusing on the individual numbers.
What I'm seeing, is numbers below the renal threshold at pre-shot. With the tests you were able to get last night, we see that Martha dropped down to 90, into those nice green numbers. Fantastic! The Lantus is working to bring the BG levels down and into nice healing numbers.
I think you have been discouraged and not seeing that the insulin you have been giving Martha is working better than you expected. That is because you have only been getting a tiny piece of the picture with those pre-shot only tests. By testing mid-cycle, you are getting a much better picture of how well the insulin is working. Pretty darn good from what I see!
If you are able to get some other mid-cycle tests, as your work and life responsibilities allow, you will get a better picture and
know how much good you are doing for Martha.
Hang in there, OK?