What! Addressing JWHW as father!
And it gets worse St Paul talks of praying using the word "Abba" (or "Papa") (Romans 8:15).
Surely not the way to address the God of Heaven to whom we give 'Honour, Respect' and does not delight when His name is misused.

It gets worse in English were some Christian groups use 'thee' or 'thou' when addressing God. At first glance this might be seen as a sign of respect or a misguided view that it's the language Jesus used! However, there is some overlap with the French 'tu' with its implications of intimacy, contempt or addressing social inferiors - surely not the way address YWHW!

What did Jesus say?

  • ... your heavenly Father ... (Matthew 6:26).
  • ... your Father in heaven ... (Mathew 18:14).
  • ... your Father is ... (Luke 6:36).
  • ... your Father has ... (Luke 12:32).
  • ... my Father's house ... (John 14:2).
  • ... the Father himself loves you ... (John 16:27).
  • ... your Father in heaven ... (Matthew 7:11).

With one exception Jesus used the word 'your'. In John 14:2 the word 'my' emphasises that He knew what He was talking about and could be trusted.
See John 16:27 "... the Father himself loves you ... and sent me ...".

Addressing God as Father implies recognition (belief / faith) that he takes an active interest in human affairs, in the way that a father would take an interest in his dependant children and act in their best interests.

Was your father like that?
Do you think God does not take an interest in you?
Do you think God does not act in your best interests? (Genesis 3:4-5)
Do you think it is too big a leap for you to approach God as Father?

Jesus declared "The hairs on your head are counted ... you are valuable ..." (Luke 12:7, Matthew 10:30).

Look at the names of God previously mentioned in this series - they express His character.
Look at the characterstics of Heaven I mentioned.
Look again and fall into your Heavenly Father's arms.

To many the mention of 'father' brings pain - turn to your Heavenly Father for healing.
We are all 'damaged goods' but His will for you is restoration - not destruction (Hebrews 12:13).

Abused? - then forgiveness and 'honouring your father' may seem out of reach. Forbidding access to his grandchildren may be the right thing to do. But, do it out of wisdom and for protection, not out of spite, not digging the knife in when you say no - that is how forgiveness can be outworked. When there is no contact / communication, and it maybe best to keep it that way, you can still forgive by praying for the offender. You may find this prayer of blessing useful - it covers everything, it is not manipulative, not demanding that you see the outcome but places the offender in God's capable, just, righteous hands:

Bless you in the name of Jesus.
To know God,
His purpose for your life,
and His blessings on you
and your family
and the situations of your life.

Still too difficult?
Explain how you feel and leave it to Jesus. His shoulders can handle it.

Maybe you can approach God as Creator, King, Lord, Ruler, Master but as mentioned earlier Father seems inappropriate, lacking honour or respect.
The prayer Jesus taught his disciples, on which this series is based, ends with the words 'For yours is the Kingdom, the power and the glory forever' (Matthew 6:13). There is no conflict here for that last sentence immediately follows the request 'Deliver us from evil'. In dealing with evil we can 'pull rank' and declare we are Children of YHWH, Jesus is the King of kings and Lord of Lords. But when we approach God, purchased by the redeeming work of Calvary, we can enter His presence with the words 'Father'.