Hello Jd, I think it's inevitable that when you change insulins there's going to be a bit of a steep learning curve while you get to grips with it. Firstly, the 1.7. That is dangerously low. Have you been given advice on how much Toujeo to start off with? If you hadn't got any other insulin on board at the time, it does sound like you'd taken too much. Half a pack of glucose tabs and porridge would probably spike me into double figures, but it's very easy to overtreat a hypo when you start from a very low figure. What happened later? Did you start to level out, or were you chasing lows all day? Probably worth discussing your figures with your health care team, who should be on hand to sort you out as you effect the change.
It might be worth your looking at the pinned thread at the top of the Newbie's section. I know you're not a newbie to insulin, but there's some good links there to articles on basal testing, etc, which you might find useful. A book I found particularly useful was 'Think like a pancreas' other people swear by the Ragnar Hanas book for children, which is actually relevant to all ages.