Welcome to the forum, Russian95!
It is excellent that you are thinking, actually thinking, using the mind that God gave you to use, about whether Lee's teachings hold up or not!
You are asking for input of what you wrote....specifically related to you possibly sitting down and talking to "saints" about it. If I try to put myself in your shoes, the first thing that comes to my mind is this: they won't care about what any theologian says or what BH Stack Exchange says or anything like that. If you are going up against Witness Lee's ministry, using ANYTHING from "Christianity" will be like using a wet noodle to hammer in a nail. Remember, the LC has been called a cult for years, and the local church both rails against "Christianity" and has been railed against BY "Christianity". Telling them that what Witness Lee teaches is called heretical by someone in that same "degraded Christianity" won't have any effect on them and will only close their ears to you and make you "poisoned" in their minds that much quicker.
In my opinion, for whatever it's worth, the best you can do is pit Lee's doctrines against the Bible itself and against logic/reality itself. They may still think you are poisoned, but you will give them a good dose of cognitive dissonance because inside they will be uncomfortable because they know they are disagreeing with the Bible, and not just with "evil Christianity."
(I'm not sure how many of the posts on this forum you've read.....I currently don't hold to the doctrine of the Trinity myself, but from what you've written it seems like you do, and you will be speaking to people who do....so I'll respond to you from within that framework. I will keep my own questions/issues with the Trinity out of it in my response.)
For example, in The Experience & Growth in Life, Lee says this:
Incarnation is God entering into man to mingle Himself with man, making Himself one with man. God was incarnated in the man Jesus Christ. He is a wonderful person, a unique person, with two natures. He has the divine nature and the human nature, yet these two natures do not stand separately; they are mingled together. He is the unique God-man.
The two natures of Christ being mingled together can be illustrated by tea and water. Tea is composed of two elements: tea and water. When we say that we are drinking tea, we actually are drinking tea and water. Therefore, we can say that we are drinking tea-water. God can be likened to tea, and man can be likened to water. As tea and water are mingled together to make tea-water, God and man were mingled together to make a God-man, the Lord Jesus. This God-man is the mingling of two elements, two natures, into one entity without a third nature being produced. In tea-water the two elements of tea and water remain distinct but are not separate. They exist together in a mingled way. It is the same with the Lord Jesus Christ as the God-man with the two natures of divinity and humanity.
But wait, wait, wait.....the Bible doesn't say "God entered into man to make the Lord Jesus." I mean, what Witness Lee is describing with his tea/water example, is a situation where you have God (tea leaves) and you have a regular man (water), and they got swirled together to create Jesus, a God-man (tea-water).
But who is the regular man who God swirled with? Where did that man go post-swirl? This is totally unscriptural.
The Bible says in John 1 that "
the Word became flesh". One thing became another thing.
I would also look at Philippians 2:5-8 (ESV)
5 Have this mind among yourselves, which is yours in Christ Jesus,
6 who, though he was in the form of God, did not count equality with God a thing to be grasped,
7 but emptied himself, by taking the form of a servant, being born in the likeness of men.
8 And being found in human form, he humbled himself by becoming obedient to the point of death, even death on a cross.
The Greek for "form" there is "morphe", which means "form, shape, or outward appearance". It's the same word used in Mark 16:12 after Jesus' resurrection and it says He appeared to them "in a different form".
Whatever form He was.....He took another form when He was born on earth in the likeness of men.
None of these descriptions of the incarnation, word becoming flesh, form of God taking the form of a servant/human, none of those are anything like tea leaves and water being mixed together to make tea.
It literally says that Jesus "came from heaven" (John 6 re: the bread of life), and that Jesus "came from the Father and entered the world" (John 16), that "since the children have flesh and blood, he too shared in their humanity..." (Hebrews 2). It seems to me that it is much more like a caterpillar morphing (there's that word "morphe") into a butterfly than it is taking tea leaves and water and soaking tea in water to make tea-water. Actually what I think it is, is simply a being with a spiritual body clothing itself with our earthly flesh/blood body. Either way, nothing the Bible gives us by way of description is like mixing tea leaves and water.
I personally think that the transfiguration of Jesus in Matthew 17 might have been a brief glimpse on His part of what He really looked like before taking on human flesh, but I'll leave that be......
Not sure if any of that helped, but I better stop here for length. My main point is.....pit Lee against the Bible, not against any other teachers.
Trapped