Maybe it's me,.. I'm not getting all the hysterical reaction here or picking up on any abuse. Not by Catholic standards.
We're trads and our marriages are not modern style and should certainly not be feminist leaning. That poison in even a small dose will undermine the sanctity of marriage and family.
In an effort to fully understand your particular situation, let's dissect:
My DH is very very unmotivated to study the Faith and constantly asks me questions and often wants me to research it for him.
So do it. You are projecting that he is slothful and unmotivated. There may be other reasons. Have you asked him? It may be as simple as that he sees you as holier than himself and respects your thoughts on spiritual issues. Many husbands feel that way about their wives, it's a beautiful compliment. He is depending upon you to help him for some reason, so do it.
He is well into his middle age so it's not a problem of youth. I'm also worried that he shows more interest in studying about heresies rather than learning what the Church teaches.
I find that understanding heresy helps my faith. We all have particular interests when studying Catholicism. Don't pick on his, unless he starts acting heretical :dancing-banana:
His lack of knowledge is rudimentary--he doesn't know what the holy days are, when to fast/abstain, sacraments, etc.
God gave you to him for a reason... what a tremendous opportunity for you to obtain grace, helping your husband to be a good Catholic. Do you know how many wives would trade places with you? To have a husband who is at least trying? Big deal, that he needs you to help him remember things. Then HELP HIM. KEEP HELPING HIM LOVINGLY.
Being sweet didn't work. Being direct didn't work. I recommended the Baltimore Catechism but he said that was for children. He spends a lot of time on Catholic forums so the problem isn't lack of time.
I detect an uncharitable attitude. "Being sweet didn't work"... so you stopped being sweet? Because he needs you to save his soul? This is a burden for you? I'm interested in how Our Lord will address this with you at judgement.
What to do????? Should I quit worrying about it?
YES. Good Heavens, yes. Do your duty to your husband.
It's embarrassing to me in front of the children because they know he's a bit spiritually dense.
Embarrassing? What should be embarrasssing to you is that your children are picking up on your attitude. You are annoyed that he needs you to help him. Why not include the children in his instruction? When he asks you a question, if they are around, turn to one of them and say "John, your father is unsure of what day to fast this week. Can you help him?" Do it respectfully and lovingly at all times. Do not betray impatience. Laugh lovingly and hug him when you remind him for the 99th time that, yes, we fast on Friday, or whatever. It's all about your attitude and delivery. God has chosen you to be with him and this is who he is. If he is to change, God will handle it, but your duty is to serve your husband.
A critical element of serving your husband is to ensure your children respect him, so don't you dare convey your impatience or your attitude that your husband is "dense" to your children. Talk about poison to the family!