I hope you won't take the Zaleplon, its called a non-benzodiazepine but it acts in the brain in a similar way to benzo's and it's half life is so short you'll develop interdose withdrawal symptoms. I know about this first hand because after my cold turkey from Klonopin I started taking Ambien and suffered horribly until I stopped taking it. I'm horrified your psychiatrist recommended it, it shows me he has no idea what he's doing.
I feel you're undermedicated on the Ativan, you were taking 1.5 mgs then tapered to 0 then reinstated at .50, its not enough but if you hold longer, your body could eventually stabilize, I don't know.
Mornings are pretty much bad for everyone around here, they describe feeling better as the day wears on, some say it has something to do with cortisol levels.
I don't know anything about Mirtazapine only that we have many members trying to taper off of it and it's not pleasant so keep this in mind.
Many members can taper from Ativan directly but some do switch to Valium but that can be rough too. Would dosing more often help get you through the day a little easier?
Please don't consider just stopping one of your doses of .25, your taper needs to be slow so you can stay functional, you know what happened last time.