Slow acting insulin not lasting?

It sounds to me that your slow acting insulin needs to be split, one injection in the morning and one in the evening as you seem to have too much insulin acting in the morning and not enough acting in the evening. Speak to your diabetes care team, many people find that splitting the dose gives better results.

It depends how recent the split was, and how accustomed you are to altering your dose.

Changing reigimes like that will be difficult. It will be a while before you get the right doses and timings.

I'd give it a month to settle down, get used to the day to day stuff. A lot of people simply need more insulin with different meals.
What do you eat for breakkie / lunch? If you have carbs in them, your long acting may be set to high if you don't need short acting.

As long as your readings are okay, i'd give it three weeks / a month to get used to the reigime. Keep contacting your team, see if they have any advice. But give it time, as it is a big change to get used to.
Good luck