Every single thing, you say?
From the start.
Bonus, Adjective: Unexpected good circumstance. (hopefully in-discussable)
What you are looking for is Bona; Adjective: Plural form of bonus. (This is indeed the word he should have used if he wanted correct latin grammar. I'm open for the possibility that there's some sort of grammar trick cheating me here, I haven't actually used my latin for a long time.)
While Boni CAN be neuter plural for bonus it makes no sense in the sentence.
As his sentence is constructed his Boni can ONLY be a noun.
Prove how his use of Boni can be ANYTHING other than a noun using proper grammar.
Tell me again how I am wrong in everything i said.
You are very confused.
First of all,
in Latin you can use an adjective as a substantive with great freedom.
In English, this is irrelevant; "bonus" is an English noun.
Let's go over Latin declension, shall we?
"bonus, -a, -um" is an adjective meaning "good". Used as a substantive, it means "a good [man/woman/thing etc.]"
The masculine singular nominative of this adjective is "bonus".
The feminine singular nominative of this adjective is "bona".
The neuter singular nominative of this adjective is "bonum".
The masculine plural nominative of this adjective is "boni".
The feminine plural nominative of this adjective is "bonae".
The neuter plural nominative of this adjective is "bona".
"Bona" is the plural form of "bonum". "Boni" is the plural form of "bonus". "Bona" is not the plural form of "bonus."