When Archwizard's Spellcraft says you don't gain more 10th level spells by leveling up, I thought it was saying that the 2 spells added to your spellbook couldn't be 10th level. But now I see that the cleric's Miraculous Spell has the same wording, and that class doesn't rely on a spellbook the way wizard does. Does that mean the sentence is just an explanation that you get only the one 10th level slot and you aren't getting more by leveling up (except with Archwizard's Might)?
Additionally, Archwizard's Spellcraft says you cannot use the slot for abilities that either give you more spell slots or let you cast spells without expending spell slots. Does the Drain Bonded Item free action count as such an ability? Let's say I prepare Time Stop into my 10th level spell slot and cast it, and I later find myself in another encounter where Time Stop is helpful. Since Time Stop is a spell I prepared today and that I already cast, does that mean it qualifies for Drain Bonded Item? Or does the fact that I prepared that Time Stop into a 10th level slot disqualify Drain Bonded Item from being used?
When Archwizard's Spellcraft says you don't gain more 10th level spells by leveling up, I thought it was saying that the 2 spells added to your spellbook couldn't be 10th level. But now I see that the cleric's Miraculous Spell has the same wording, and that class doesn't rely on a spellbook the way wizard does. Does that mean the sentence is just an explanation that you get only the one 10th level slot and you aren't getting more by leveling up (except with Archwizard's Might)?
Your spellbook is not limited in the number of spells that you can learn and store in the book. The restriction on the number of 10th level spell slots is for just the spell slots that you prepare spells in and cast from.
Additionally, Archwizard's Spellcraft says you cannot use the slot for abilities that either give you more spell slots or let you cast spells without expending spell slots. Does the Drain Bonded Item free action count as such an ability?
Drain Bonded Item is exactly the type of ability that can't be used with 10th level spell slots.
Your spellbook is not limited in the number of spells that you can learn and store in the book. The restriction on the number of 10th level spell slots is for just the spell slots that you prepare spells in and cast from.
So regarding this sentence: "Unlike with other spell slots, you don’t gain more 10th-level spells as you level up, though you can take the archwizard’s Might feat to gain a second slot." This sentence is only about the number of 10th level spell slots I have? It's not stopping me from getting 2 free 10th level spells for leveling up?
Yes, at level up you still get two known spells of any level you can cast, including level 10.
"Unlike with other spell slots, you don’t gain more 10th-level spells as you level up, though you can take the archwizard’s Might feat to gain a second slot."
Yes. The rule writer used the wrong game term in one place. The other two places are talking about spell slots. And that is what it should be stating in that marked spot also.
Nothing is preventing you from learning 10th level spells and putting them in your spellbook - either automatically when leveling up, or through the Learn a Spell activity. You can have 7 10th level spells known if you want to spend the time and money on it - with or without the Archwizard's Might feat.