Glucose levels

@purrpleness sorry to read that you are struggling with your diabetes management.
It sounds to me as if you have not been told how the two different insulins work and why you take them. Please excuse me if you already know this:
- the long acting insulin you are taking is your "basal" insulin. I think of this as my "base insulin". Throughout the day and night, our liver drips glucose into our blood. The purpose of this basal insulin is to "mop" up this glucose from your liver. In the absence of anything else that could affect your blood sugars (mostly, although not entirely, this will be what you eat and drink), with the correct basal dose, your blood sugars should remain relatively flat. The best way to see this is what happens overnight when you are asleep and not eating.
- the fast acting insulin is your "bolus" insulin. This is used with the food that you eat (and any correction doses). Any carbs that you eat are converted to glucose. It is common to "carb count" and adjust your insulin according to how many carbs you are eating. You mention that you have not been told this so your insulin dose is likely to be a guess.

Unless you are on a low carb diet, it is common for the two most carby meals of the day to be breakfast, when you eat cereal, and lunch when you have sandwiches. I would assume that your evening meal has less carbs which is why you do not see your BG numbers rise so high.

Some DSNs encourage carb counting and dose adjustment as soon as possible whereas others seem to think it would confuse us too much.

I recommend talking to your DSN about carb counting and insulin to carb ratios which you will use to calculate your dose of fast acting insulin. If they will not "allow" this, you could ask how many carbs your fixed dose is based on.
In the meantime, it would be useful to get into the habit of calculating how many carbs there are in your meals. Apps and books like Carbs and Cals will help with your carb counting. It may seem hard work but you will soon learn the carb content of common meals - most people eat the same thing for breakfast and lunch.

I could expand on variations and timing and more but for now, I will just say "don't expect perfection" even if you carb count. I have only mentioned the most common contributors to our BG readings.