Your goal seems to be to have the NPC profit every time it is cast. It looks like you value spells without material components, but why not embrace (expensive, consumed on use) components?
Instead of making and selling scrolls, the easiest way to charge someone every time they cast the spell is to build the spell with an "expensive" material component you have monopoly over. This is something the Wizard can do himself at any level, and will fall within/sidestep the legality concerns by having built in rights management (punishment is irrelevant if it simply doesn't work without the requisite consumed-on-use license token).
No you cannot transfer spells prepared as a Cleric into your spellbook
Just above the text that you reference, the sidebar in the PHB explains
When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a level for which you have spell slots and if you can spare
the time to decipher and copy it.
The fact that the book explicitly says that it contains wizard spells is the killer here. Spells that you prepare as a cleric are not wizard spells. They are cleric spells, even if they are on the same spell list.
We know this because of the rules for multiclass spellcasters (PHB pg. 164)
Each spell you know and prepare is associated with one of your classes, and you use the spellcasting ability of that class when you cast the spell. Similarly, a spellcasting focus, such as a holy symbol, can be used only for the spells from the class associated with that focus.
From this, we establish that your prepared spells as a cleric are "Cleric Spells" in that they are prepared as a cleric, and cast as a cleric; not as a wizard. And your prepared spells from your spellbook are "wizard spells" for a similar reason. Even if the two appear on the same spell list, each spell you have prepared is associated only with one of your classes.
The PHB then goes onto explain that when copying spells from spellbook to spellbook:
This is just like copying a new spell into your spellbook, but faster and easier, since you understand your own notation and already know how to cast the spell.
If copying from book to book is the same as adding new spells except faster, then we know that you can only transfer over wizard spells since you can only copy new wizard spells into the spellbook.
Finally, As you have pointed out:
you can use the same procedure to transcribe the spells that you have prepared into a new spellbook
The procedure in question is the same as copying over a new spell, or a spell from one book to another. Both of these processes require wizard spells to work. Thus, even though copying a spell down from memory doesn't specifically add any new restriction, it doesn't explicitly lift the general limitation on the procedure; the precondition that the spell in question is a wizard spell.
One of the best magic items for increasing survivability is the periapt of wound closure. It automatically stabilises you at the start of your turn if you're dying, and hit dice recover twice as many hit points.
With this item, if you ever get knocked unconscious, you only need to survive until the start of your next turn, at which point you will stabilise. This will prevent your character from dying to death saving throws, but your party will still need to defeat the encounter to survive.
It will also give you a lot more bang for your buck in terms of recovering HP on short rests. You effectively get twice as many hit dice, allowing you to keep going for longer without worrying about HP.
And the item is definitely "near your level", the periapt of wound closure is an uncommon magic item. If your DM follows the guidelines in the DMG, you should be able to craft it.