How to get husband's attention, romance and intimacy?

It looks like you've been deprived of the affection and companionship that comes with a marriage. You got married at a tender age when all of this must have been so much more important and not having your husband's attention and love must have been very disheartening for you.
It's worthy of appreciation that you've been able to persistently try to win him over and still put in effort after all this time and not give up, it takes a lot of strength to stay in such a marriage.

In my opinion, initiate a serious and focused conversation with your husband about the lack of romance and intimacy in your marriage. Given that he is away most of the time, explicitly voice that you would like to spend whatever little time you get in a memorable way. By way of this conversation, also ask him what is missing for him, why he has been distant in some ways and what is it that he wants from this marriage and from you?
None of these questions need to be harsh or accusing. As his partner, you can put these across in a matter-of-fact manner and let him know that you are seeking some answers to understand your relationship with him. Try your best to be firm about what you're looking for and don't hesitate in asking for what you need. It is a relationship that both of you got into knowing that it means commitment to each other. Think about what you want to say and ask him, write it down for better clarity and choose a good time, when you know that you both are unlikely to be disturbed and go for it.

It is possible that being apart for so long has taken over and the physical distance has set in a little more strongly between you two, causing emotional distance as well.

The nature of this conversation can tell you a little/ a lot of what you need to understand and know about your relationship. Maybe he's unable to communicate with you and hasn't considered the impact his behavior is having on your marriage, which is why an open and serious conversation without excuses is necessary. If you have a family member or friend you trust, see if they can be part of the conversation to facilitate it in case you need the assistance.

I hope this brings about some clarity on your relationship in your mind and helps you bring stability into your marriage.