Hi Georgina,
no, faith is not about certainty, it is about trusting from within the heart.
Your scenarios are a little bit conspiracy-like. You have to take into account that in the times of Jesus, the written word was the only possibility to conserve cultural contents. Especially religious contents were such holy that the translaters and copy-men got castigated when they wrote a single incorrect sign down. There was a whole class of such men that were only consumed by copying these texts and were explicitely educated for this holy service.
Since the writers of the gospels were Jews too, they couldn't allow themselves to lie about anything they write. Even if they did, every reader of their "lies" must have laughed out loud and the gospels couldn't spread like they did. Writing for example that Jesus healed many people whereas your conspiracy-theory suggests that he didn't healed a single person makes no sense in the times after Jesus died. Remember that he walked through half of Palestine more than once within 3 years. Therefore, according to your theory, there must have been many eye-witnesses, but none of them saw an actual healing. According to your theory, these "healings" must have been just rumours and none of the people that met Jesus have ever seen a single healing from him. Worse: even his disciples never saw a single healing done by him.
Take for example the gospel of Luke. He writes in chapter 1, verse 3 that from the beginning he investigated everything about the "case". It may be that he really investigated and interviewed all the people and according to the results, he wrote down his gospel with good conscience. The problem here is that everything he researched must have been based on lies from eye-witnesses (still living) or other people. For this scenario we have to assume that every man and woman lied to him in respect to the important things that could qualify Jesus as the real Messiah. Or alternatively, that every man and woman he spoke with didn't really know what they are talking about (because they only heard that Jesus did this and that but never saw it directly). Even with some good will I would estimate such a scenario as very unlikely. It would require that all these people have fooled each other. Remember that the majority of the Jews didn't accept Jesus as the coming Messiah. The Jews weren't idiots or fools. If Jesus didn't heal anybody in the temple, the Pharisee would have soon spread the word that Jesus never healed anyone in their temple. Now, according to your theory, this may have been historically the case. But then, the gospels simply lie about these facts and if not the gospels lie about them, the disciples of Jesus must have fooled everybody who trusted them and their words.
Let's go to some other aspects of the gospels. Jesus said that the temple will be destroyed. 70 A.D. the temple was destroyed by the romans. They surrounded Jerusalem and crucified many people on the hills. The gospels said that the believers should be aware that this would come to pass and they should flew to the mountains. Thanks to God, in about I think 67 or 68 A.D. the sourroundings of Jerusalem was paused because Nero died and the man who was in charge for the surroundings wanted to be the next Emperor of the roman Empire. This gave the believers the time to go out of this city.
The next prophecy says that the Jews once will return to their homeland in the endtimes after having been spread all over the earth having no homeland after the destruction of the temple. Also this prophecy has been fullfilled. Since 1890, many Jews went back to their homeland (from Russia) and tried to recultivate their land. Even more: After two world-wars that tried to efface the Jewish race from the earth, these Jews officially became back a part of their homeland. Since at that time the land was highly desolate and infested with malaria, they had much to do to reagricultivate it to live from it. As you know, they turned the land into a kind of Garden Eden by planting Millions of trees and plants. Also this was prophecied in the old testament.
If you take together all the fullfilled prophecies and make a calculation about the probability for them to all occur according to the scriptures, you will find that the probability for that is much to small to ever occur as a humanly fabricated conspiracy. Or put it another way: there must be something very strong that leads humanity to execute such a mindblowing conspiracy. And I believe that this "something" is the reliable word of God, that the healings by Jesus took place and that denying them is a conspiracy of human pride. We think to know everything about nature. Therefore we exclude miracles and godly intervention. But do we really know everything about nature - or do we only believe that we know everything? And according to which sources do we believe that we know everything about nature? Isn't it true that these sources are not scientifical, but personal and philosophical opinions about the things we already found out about nature (laws of nature etc.)? Who says that what we already found out must be all there is? Couldn't it be that the spreading of the belief that the laws of nature must be considered as the modern version of a universal God is a similar conspiracy as you suggest for the case of Jesus, a conspiracy based on rumours and personal philosophical beliefs, but not on provable facts?