I found in the book 'Zot Zikaron' by the Chozeh of Lublin (Warsaw, 1883, page 44) that he himself addressed this question. This is his wording: "Our Rabbis of blessed memory said, 'A person's sustenance is as difficult as the splitting of the Red Sea,' and this is puzzling. Is the splitting of the Red Sea difficult for the Blessed One? After all, He created the world with a mere utterance, which is an even greater miracle, something from nothing, and He does not tire or grow weary, etc. Moreover, it should have been said 'like the Exodus from Egypt,' which was certainly more difficult, as we find that we are commanded to always recount it. And during the first days of Pesach, we recite the full Hallel, but not on the seventh day of Pesach. As it is written (Deuteronomy 4:34), 'Or has any god ever tried to go and take for himself a nation, etc.,' indicating that the primary event was the Exodus from Egypt, etc."

And the Chozeh answered this question as follows, and this is his wording: "And the truth appears to me, given to me by the Blessed One, that it is stated in the Zohar (Beshalach 52b), 'The splitting of the Red Sea is dependent on the Ancient One.' What is this? It is written, 'Why do you cry out to Me? Speak to the Israelites and go forward' – the term 'go forward' (in Hebrew 'sa') can mean 'to remove oneself from brotherhood' (Rashi on Genesis 37:17). Similarly, 'they removed the gate' (Judges 16:3). The explanation is to divert their minds from it, not to think about it, but to rely on the Blessed One, as He wills is good. And this is 'in the Ancient One,' as in 'those weaned from milk' (Isaiah 28:9). And as in 'he moved from there' (Genesis 12:8). And through this was the splitting of the Red Sea, and this is like something from nothing. And this 'a person's sustenance is as difficult,' means if a person's sustenance is difficult for him, he needs to behave like at the splitting of the Red Sea, not wanting it specifically like this, but thinking as the Blessed One wills, etc." End of quote.

Thus, in truth, there was no difficulty for the Blessed One in the splitting of the Red Sea, and the wording of difficulty in the sayings of our Sages only refers to sustenance, and concerning a person, they said: if sustenance is difficult for a person, his remedy and correction are to behave like at the splitting of the Red Sea.

However, this does not resolve the straightforward meaning of the saying, which implies that by way of comparison, the difficulty of sustenance is like the difficulty of the splitting of the Red Sea, and if so, it had a difficulty, as it were.