Isn't the husband somewhat responsible for the wife's faith / salvation since God made the husband the head of the household spiritually??
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He is absolutely not responsible for the wife's salvation or the wife's relationship with her heavenly father in any regard. She is to have a direct relationship with her Savior, outside of her role as a wife.
As another poster said, Jesus is the author and finisher of your faith. Galatians teaches us that God is not a respecter of persons and that all are viewed the same by him, whether bond or free, male or female, etc.
There are some patriarchy groups who teach that the wife is to obey the husband to the extent that if he commands her to sin, she must do the sin and that God will not hold it to her account but to his. That is a doctrine of the devil; it is a perversion of God's word and is not supported anywhere in the Bible.
Ok so we are both Christians but hes doing a very lazy effort of the spiritual leader as the duties God has given him as my husband. He always says we are going to start doing devotionals but never does we never pray together at all the last time was 5yrs ago at our wedding which is sad and pathetic and even when I try to get him to sit down to do a devotional w me he always makes some excuse as to why he cant. I don't know what to do anymore.
Using the business end of the Bible to compel someone to give in to you (whether for devotions or for more sex, or etc.) usually does not lead to long term success.
When that happens, your taker is demanding a concession from their giver, which they may reluctantly give. However, after some time their take will rise up to say "Enough! It's my turn to take now!!" and this can often be a catastrophic fight. Takers don't really care what the other person thinks or feels when they are enforcing a rebound.
It's better to sit down together and brainstorm what spiritual connections he would be enthusiastic about. Have your takers negotiate with each other until an action plan that you are both enthusiastic about can be reached.
Here are some great articles about the giver/taker and how to successfully negotiate:
The Giver & Taker
The Policy of Joint Agreement
What would you think of printing these articles off and bringing them to your husband?
When you both are in agreement with these concepts, you could let him know that you would really enjoy meaningful connections about spiritual matters and, if he would be enthusiastic about that would he be willing to brainstorm options?
Don't constrain yourself to your way or his way. There are 100's of other ways - think outside of the box until you find one you both are enthusiastic about. You'll want to negotiate with his taker to prevent an ugly eruption down the road.