We are truly sorry to hear about the overwhelming situation your daughter is facing. We trust in the power of prayer and the grace of God to turn around even the most dire circumstances. Let's bring this situation before the Lord in prayer and seek His will according to His word.
Firstly, we want to address the living arrangements and relationships. The boyfriend of your granddaughter with four children is not working due to anger and anxiety issues. The man of the household must follow the biblical command to work and provide for his family. Apostle Paul says in First Timothy, "But if anyone doesn’t provide for his own, and especially his own household, he has denied the faith, and is worse than an unbeliever." It is clear that this situation should not continue, and this behavior should not be enabled. We pray for his healing from anger and anxiety, that he may become a productive member of the household and society, seeking first God's kingdom and working to provide for his family -
"Turn away from evil, and do good.
Search for peace, and pursue it.
For the eyes of the Lord are on the righteous,
and his ears open to their prayer;
but the face of the Lord is against those who do evil." 1 Peter 3:11-12 WEB
We also encourage your granddaughter to seek the Lord in this. Living with a man who is not her husband and not doing his part is not aligned with God's will for her life. The fact that there are children involved who are witnessing this behavior and may follow in the same footsteps to their detriment is alarming. We pray that they both come to repentance and embrace God's design for their lives and their family.
Concerning your daughter taking care of a household of so many people, we encourage her to look to God for strength and wisdom. We pray that God will raise up your daughter and give her the strength to handle all that she is responsible for. God can make a way where there seems to be no way. He can provide for her needs in ways that are beyond our comprehension. We have seen God work miracles time and time again, and we trust that He will do the same for your daughter.
"Ask, and it will be given you. Seek, and you will find. Knock, and it will be opened for you. For everyone who asks receives. He who seeks finds. To him who knocks it will be opened." James 5:14-15 WEB
Our hearts go out to you as you deal with your own medical issues. We pray for your healing and that God will give you the strength to support your daughter as only a loving parent can. We thank you for your service to this country and for your willingness to give your disability income to your daughter. May God bless you for your sacrifice of love.
"But my God shall supply every need of yours according to his riches in glory in Christ Jesus." Philippians 4:19 WEB
Finally, we want to remind everyone that it is only through the name of Jesus that we can come before God and ask for these blessings. It is by His blood shed on the cross for our sins that we are made right with God and can come boldly before His throne of grace. We did not see any mention of Jesus in your request. We strongly encourage you to believe in Jesus Christ as your Lord and Savior. He died for our sins, He was buried, and God raised Him from the dead. He offers us eternal life as a free gift. It is only through His name that we can be saved.
"who [Jesus] existed in the form of God, didn’t consider equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being made in the likeness of men. And being found in human form, he humbled himself, becoming obedient to death, yes, the death of the cross. Therefore God also highly exalted him, and gave to him the name which is above every name; that at the name of Jesus every knee should bow, of those in heaven, those on earth, and those under the earth, and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father." Philippians 2:6-11 WEB
Let us pray together:
Heavenly Father,
We come before You in the name of Jesus, lifting up this family to You. Lord, we ask for Your healing touch on the boyfriend struggling with anger and anxiety. We pray that he will become a productive member of the household, seeking first Your kingdom. We rebuke the spirit of idleness and lack of responsibility and command it to go in Jesus' name. We ask that You will raise up the daughter and her mother, giving them the strength and wisdom to handle all they are responsible for. We pray for healing for her and for her father. We ask that You will provide for their needs in ways that are beyond our comprehension. We pray for this family to have a supernatural financial miracle. We ask that You will bless them for their sacrifice of love. We pray for the children in this situation, that they may see the glory of God in their family and follow Jesus all the days of their lives.
In Jesus' name, we pray. Amen.
Prayer Focus: God, Thank You. Thank You for loving me. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
