Since the Christian God is made of Spirit, and cannot see, hear, or feel, how does He know He exists?

First tell me where you got the idea that God cannot see, hear or feel.

Then tell me where you got the idea that only things with physical eyes and ears can hear or see.

Meanwhile, I'll go look up that YouTube video about all those dimensions above the four in which we reside.

Unable to answer this.

"the Christian God is made of Spirit" - TRUE

"and cannot see, hear, or feel" - FALSE

Revise this so we can see what you are trying to ask or say

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Looking at your revised question, it is still rather senseless. You vacillate between our seeing him and believing he exists, and his seeing Himself and knowing he exists.

Perhaps this is a very existential question, in which case you are a secret genius

Considering that the Christian God is omniscient, omnipotent and omnipresent, what would give you the impression that He cannot see, hear or feel? He declared that He is a jealous God, that's a feeling. He hears our prayers...and He sees our sins and good deeds.

I never understood when people try to explain how God works. Most people can't describe in detail how a microwave works, but yet they want to explain an all powerful God far beyond our understanding. How does that make any sense?

You need to learn how to ask questions first. You have to ask one question at a time, not 3.