To see Jesus is to see the Father. Since the disciples always see Jesus, they always see the Father. Scripture also said that the disciples did not only see Jesus but they also heard Jesus and touched Jesus. Does that also mean the Father has been heard and the Father has been touched by the disciples too? It is mostly likely that the vision of the Father in Jesus is not referring to the literal physical outward appearance of Jesus but to Jesus' actions based on context ("the Father who dwells in me does his works"). It is the works of the Father that is seen in Jesus and that is how the Father is seen in Jesus. It is also evidence why Jesus is "equal with God" in John 5:18 because in context in verse 17 it says that Jesus works and the Father works. They are both working simultaneously and that's how they are said to be equal (Grk. ison) in the text. And in verse 19, John limits the abilities or works which Jesus can do: Jesus can do only what the Father does. For instance, creating all things (John 1:3).
To say something to Jesus is not to say something to the Father because when someone speaks to Jesus, they speak to Jesus (not the Father). When Thomas said to him (to Jesus alone): My Lord and my God. It does not mean Thomas said to the Father. Both grammar and context affirm that Jesus alone is the antecedent of the singular pronoun "him" in v. 28.
To say something to Jesus is not to say something to the Father because when someone speaks to Jesus, they speak to Jesus (not the Father). When Thomas said to him (to Jesus alone): My Lord and my God. It does not mean Thomas said to the Father. Both grammar and context affirm that Jesus alone is the antecedent of the singular pronoun "him" in v. 28.