"There is sure to be" has an element of assumption about it. e.g. "There is sure to be a fish in the pond". This means that it is very likely to be fish in the pond but there is a chance there is not.
"There sure is going to be (fish in the pond)" is a definite statement with no chance of the opposite being true.
Your second statement is correct. To remember the correct usage of He, Him, His, She, Her, Hers, They, Them and Theirs it's important to learn about "Pronouns"
Pronouns are used to replace Nouns to avoid repeating yourself. e.g. "Jack likes his eggs boiled". The Noun is "Jack" and the pronoun is "his"
Simple rules for pronouns:
He, She and They are used when pronoun is the SUBJECT of the sentence e.g. "He likes going to the movies". The SUBJECT is what the sentence is about.
His, Hers and Theirs are POSSESSIVE pronouns. These are used when you're talking about something belonging to the person e.g. "This Hat is hers" or "These potatoes are theirs"
Him, Hers and Them is used when the pronoun is the OBJECT of the sentence. The Object in a sentence is something that is effected by the rest of the sentence, usually by the subject or a verb and sometimes both.
In your sentence "The divorce will hurt you more than it will him":
The SUBJECT is the divorce.
Hurt in this usage is a VERB
the pronouns "you" and "him" are both OBJECTS.
So the SUBJECT is effecting the OBJECT.
"You" can be both a SUBJECT pronoun and an OBJECT pronoun.
That's as simple as I can make it sorry. It's something that requires a bit of practice and it goes deeper than what I have explained but this is a good starting point that will look after most of the common pronoun usage.