Thank you for opening your heart so honestly and for anchoring your cry in Scripture. Your longing for the nearness of God to be your good, as Psalm 73 says, is itself a work of His grace, and He hears the one who seeks Him in loneliness and asks for wisdom, revelation, and strength to walk in love.
The first foundation for all prayer is relationship with God through Jesus Christ alone. Apart from Him we have no access to the Father, just as under the old covenant no one could come directly but only through a mediator and sacrifice. The only prayer God desires from someone who is not yet His child is, God be merciful to me, a sinner. When that mercy is received through faith in Christ, the way is opened and we can come boldly, not on our own goodness but on His. If you are His child, you can come with confidence, and if there is any doubt, settle that first by trusting Christ alone for salvation. Everything else in prayer flows from that restored relationship.
You spoke of fasting, spiritual warfare, and standing against the schemes of the enemy. It helps to remember what prayer truly is. Its purpose is not to get our will done or to persuade a reluctant God to see things our way. Prayer begins with God. He makes His purposes and desires known to our hearts, we echo them back to Him, and He accomplishes what He purposed. In that cycle we learn reverence for His name and we discover that He desires to become to us whatever our need requires, whether wisdom, strength, comfort, or provision. That is why true prayer is not an attempt to change God, but to open the door for Him to do what He has already desired to do for us in love. He does not force His will upon us, but through prayer we yield and invite Him to work.
For that reason, fasting is not a way to obligate God or to earn an answer. Isaiah 58 shows that God is not impressed by outward religious activity done to make our voice heard on high. Many fast with the motive of getting something from God, as if He must then repay us. A biblical fast simply denies the flesh so that we have more time and sensitivity in the Spirit to seek Him. God already wants to bless you, not because you are so good but because He is so good, and He gives out of love, not as a reward for good behavior. To accept grace gracefully is often hard, because we try to make ourselves deserving. Come instead humbly, asking that His will be done in earth as it is in heaven, trusting that His will for you is good. You do not need to be afraid of anything God has for you. The only thing to fear is not being fully open to what He wants to do in your life.
You also asked for grace to resist the lies of the enemy and to stand firm in the faith. Scripture gives a clear order. First submit yourselves to God, then resist the devil and he will flee from you. James 4 and 1 Peter 5 teach the same pattern. Resistance is not in our own strength or with carnal weapons. The weapons that tear down strongholds are mighty through God, as 2 Corinthians 10 says, and they belong to those who have denied themselves, taken up the cross, and follow Jesus to bring glory to God rather than to fulfill our own desires. At the same time we are told to draw near to God and He will draw near to us. You asked for nearness, and that promise is for you. As you draw near in worship, in the Word, and in quiet obedience, He draws near in return. The Holy Spirit was promised to remind you of the truth Jesus taught, to give direction as you hear His voice and follow Him, and to make the love of Christ real within you.
You mentioned not knowing what to do and needing wisdom. God invites you to ask Him for wisdom, and He gives generously. Yet that asking calls for a complete commitment, not holding part of your life back or asking for wisdom and then doing your own thing. Bring the whole matter before Him, including your marriage and your child, and ask Him to align your will with His. God never solicits you to evil. He may test us, but He never tempts us to sin. The enemy, on the other hand, often suggests that we can accomplish God's good purposes apart from God's appointed way. Jesus was tempted to take the kingdoms of the world without the cross, to prove Himself by a spectacular display, and to draw people by sensational means, but He rejected every shortcut. The Father's plan was redemption through the cross, to buy back a world that had been handed over to the enemy when man yielded to him. Our calling is to walk that same path of obedience, not seeking spectacular proof but trusting the Word.
For your marriage and family, your desire to please God is the right anchor. Marriage as God designed is a lifelong covenant of one man and one woman, and intimacy belongs within it. When a marriage is strained, God's call is to seek to make it good by giving, forgiving, loving, understanding, and pursuing oneness in Christ. Continue to intercede for your spouse and your child, asking for deliverance from temptation, deception, and every lie, and for protection from evil people and from the evil one himself, as Jesus taught us to pray, deliver us from evil, and as Paul prayed that the Word would run freely and that believers would be kept from evil. The church Jesus builds will prevail, and the gates of hell will not stand against it, not because of our strength but because He is building it and He has redeemed us to live again under His gracious rule.
Do not lose heart, as Jesus urged in Luke 18, to always pray and not give up. He also prayed for Peter that his faith would not fail and that afterward he would strengthen his brothers. That is a good prayer for you and for her, that your faith would be kept and that you would be able to strengthen others. Stand in the gap as an intercessor, knowing that God is looking for those who will stand before Him for others. He knows all your ways, He is intimately acquainted with your loneliness, and He delights to give you the Spirit of wisdom and revelation, to teach you to hear His voice and to obey it.
May the Lord grant you mercy, grace, and strength to seek Him with a whole heart, to walk in love, to know more deeply the breadth and depth of Christ's love, and to see His Word go forth with power in your home. May He keep you and your family from deception and evil, remind you daily of His truth, and draw near to you as you draw near to Him, until you know in experience that His nearness truly is your good. In Jesus name, amen.