I don't mean to trample on your understanding, but I was blessed to be saved in ignorance of denominational divisions,
No worries! "Dispensationalism", as a concept, has, I think, a lot of baggage being lugged around with it.
Nothing to do with denominations. Myself, I was saved through the teaching I'd received as a very young child, when later, as a young adult, I came to realize those things were true.
Dispensation comes from Paul's use of oikonomia, the "house law", which refers
to the ways and means by which the household provides for the needs of it's members. Our word "economy" comes from this word.
If we think of the world as our household, and we the members, our most fundamental and profound need is to be revived in reconciliation to our Creator. Dispensation was chosen as a translation in the idea of "to dispense", it is a despensation, that is, the house law providing for the household.
It becomes it's own sort of doctrine in realizing that the reason Paul speaks of this dispensation is that there are variations in the ways and means by which God provides for our reconciliation and life with Him.
As you had said, and the same as in Romans 8, we don't hope for that which we see, or your words, we don't have faith in Him when we see Him, I think was how you put it. I completely agree with you here. The fact that Jesus is Personally in Jerusalem ruling mankind does change things. Before that time, we are told to trust Him, and, the just shall live by faith. Then, the command is to keep the commandments. Isaiah talks about the sinner will be the one to die young, only 100 years old!
Before Jesus came, God's way of giving grace and salvation to mankind was focused on Israel, being a covenant of commandments which if kept gave blessing, and if not, cursing. Other peoples, all we know, I think, is that God wasn't shy of communicating personally with other people, and interacting with them as groups, and faily openly.
In Christ the temporary reconciliation given by the animal sacrifice was replaced with the permanent reconciliation through Jesus' offering of His body to death. This is the change in the dispensation.
When we say, faith will be superceded by obedience when Jesus comes and rules, then this is the change in the dispensation, or, how God goes about providing for the needs of His people.
It's always wrapped around faith. Abraham is held as the example of faith, and the father of all we who believe. What did he believe? God came to him and told him he would have innumerable children, more so than the stars in the sky. Abraham believed God, and that believing, God saw that, and justified Abraham, that is, rendered him righteous. Abraham believed God, and God accounted it to him for righteousness. His faith was in God, that God's message to him was true, but that message was different than the message we receive from God today, to believe in Jesus, to receive Him. That He was The One sent to die for us, that in Him we have life.
Hopefully this gives a more clear idea of what I mean as I'm talking about dispensations.
Much love!