The ratio is 100% Holy Spirit.
We understand that our ability to understand the spiritual things of God is directly related to a dependence in the Holy Ghost teaching us.
This is true as to how we get saved...
John 16:7-9
King James Version (KJV)
7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:
9 Of sin, because they believe not on me;...and it is true after we are saved.
Now, consider the above passage, and notice that Christ foretells the coming of the Comforter, and that He, the Comforter, will convict the world of sin. We know this is a reference to the unsaved, because v.9 makes it clear they do not believe on Christ.
Now, I ask you one question: do we contribute to that with our knowledge?
The answer is no, we do not, again, He, the Comforter...is the One that brings conviction. That is the specific ministry He performs in this Age.
Now that leads us of course to the question, "Does this mean we do not need to be concerned with the level of our own understanding?"
The answer is no, because one of the things we do, when we are trying to be used of God, is of course come under obedience to all that is commanded us. And a simple command for us is...study.
I will present a couple passage relating to this, but will preface those passages with asking, "Can we be used of God to witness to people if we do not know what it is we need to say?"
One might look to this...
Mark 13:11
King James Version (KJV)
11 But when they shall lead you, and deliver you up, take no thought beforehand what ye shall speak, neither do ye premeditate: but whatsoever shall be given you in that hour, that speak ye: for it is not ye that speak, but the Holy Ghost....as an excuse not to study, but this would be, first, yanking this teaching out of it's context (which is that of the Tribulation period, not a general teaching for our Age) and secondly, ignoring other specific instructions that demand we not remain in a state of immaturity in regards to our knowledge of the Word of God.
So here are a few passages to consider:
2 Timothy 2:15
King James Version (KJV)
15 Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth.Another would be more specific:
Hebrews 5:10-14
King James Version (KJV)
10 Called of God an high priest after the order of Melchisedec.
11 Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing.
12 For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.
13 For every one that useth milk is unskilful in the word of righteousness: for he is a babe.
14 But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.Now, a few points to consider in this would be first that in view are not Christians. Might surprise you, but, those spoken to here are Hebrews (hence the title of the Book). While the Epistle to the Hebrews was written to be circulated in the Church, the warning here is specific to the Hebrew People and the Covenant of Law. So what we are not seeing here is a call for Christians to mature in understanding, but a rebuke to Hebrews who were ignorant of the First Principles of the Oracles (Word) of God. That refers to the Hebrew Scriptures, which, while the Epistles and Gospels were being circulated at this time, had not yet been put together as we have them today.
And the point is this: he is saying, basically, "As long as you have been associated with Christ you should be teaching the deeper truths of Christ, but, you have need of being taught again the ABCs found in the Old Testament."
Now, look at v.14, and see who that deeper knowledge (strong meat/more complete understanding of Christ as opposed to milk/the ABCs of the Hebrew Scriptures) belongs to: those who are familiar with the Word of God.
They have discernment "by reason of use."
So while I would agree that one can definitely witness without being some great Theologian, that does not justify a position where we might think we will be able to be the witnesses God means for us to be.
Again, salvation is wholly the Work of Holy God, and though we be used of Him in that process it is He Who brings conviction of sin. He Who enlightens.
But, if we are ignorant, or in error in our witness, we work contrary to how God has always presented His Word, which is something that is to be handled as though our very lives depend on it. Christ gave great reverence to Scripture, and He rebuked severely those who were in error in their doctrine, and warned us not to embrace the doctrines and practices of men. We should also give that reverence to the Word of God as Christ did, He being our example as to how we should view the Word of God.
And this was in response to the discussion in the text. Now on to your specific Questions:
I think so. There is no time I feel the presence of the Lord stronger than when I am witnessing. This is why I always encourage people to spend time in the Word, and spend time in discussion with other believers, in an attempt to motivate them in regards to the Word, so that they might enjoy this fellowship.
However, I can look back and see times when I witnessed in my own power. This is something that is possible too. So when I witness now, I have learned to be conscious of the Spirit and I try to allow Him to work through me.
Sometimes, yes, but not with the finality suggested here.
This is the amazing truth I have shared with a number of people often: that's why God gave us His Word, lol.
Note that discernment of good and evil is attributed to those who have put effort into knowing the Word of God (Hebrews 5:14). That discernment is something every believer can enjoy, but, not if we do not seek to further our relationship with God. If we say we want to know God better, should we not take advantage of what He has already given us?
God bless.