17b the power of the Lord was present for Him to perform healing
How is it said, the power of the Lord was present with Christ to heal? had not Christ this power of healing at all times?
Matthew Poole answers:
Doubtless he had, for he was always the Lord that healeth us. The Divine nature once united to the human was never separated from Christ, but it did not always put forth itself, being as to that directed by his will.
Yes, it is Jesus' nature to heal but only as directed by the Father's will.
But as the end of Christ’s miracles was for the confirmation of his doctrine; so we shall observe, that mostly after preaching he wrought his miraculous operations.
In this case, the miraculous healing is a sign to confirm Jesus' teaching:
22 Jesus knew what they were thinking and asked, “Why are you thinking these things in your hearts? 23Which is easier: to say, ‘Your sins are forgiven,’ or to say, ‘Get up and walk’? 24But I want you to know that the Son of Man has authority on earth to forgive sins.” So he said to the paralyzed man, “I tell you, get up, take your mat and go home.” 25Immediately he stood up in front of them, took what he had been lying on and went home praising God. 26Everyone was amazed and gave praise to God. They were filled with awe and said, “We have seen remarkable things today.”
There was another occasion that it was the will of the Father to heal everyone, Luke 6:
And all the crowd sought to touch him, for power came out from him and healed them all.
Is there some hint here that the power of the Lord was only sometimes present for Jesus to call upon?
No, the power of the Lord was always present for Jesus to call upon. It's just that there were occasions that Jesus chose not to exercise that power, Matthew 26:
53 Do you think I cannot call on my Father, and he will at once put at my disposal more than twelve legions of angels? 54But how then would the Scriptures be fulfilled that say it must happen in this way?”