These questions are pretty interesting and are basically the key point to figure out the gaps. I'll try to reply based on what I think:
1) When Freeza kicked away the blast, was it a change in effort alone, or power too?
Freeza initially said he did rise his speed when dodging Vegeta, so I tend to think Freeza (kicking Vegeta's blast) was just him matching his speed used to tool Vegeta.
2) After Freeza kicked the blast away, did he remain at that power, if it did change, or did he go back to his level that he used to outspeed Vegeta badly?
I think he remained at this power, which is a power which matches his speed used to tool Vegeta.
But this also raises a question: can you increase speed surpassing your power? I always thought this was a weird situation. How can you take speed from nothing? Look at Tenshinhan in the 23rd Budokai, he was witholding speed, whereas his power was above the speed he was using initially against weighted Goku. The same for Cell, he was just witholding speed against Goku, whereas his power was higher than that. So I could see a scenario like this:
Figher x:
Power : 100
Speed : 80
Speed inncrease : 100 (he only raised speed to match his power, that is, was witholding speed)
Fighter x:
Power : 100
Speed : 100
Speed increase : 125
^That's a scenarion which could never happen imo. How do you increase speed, surpassing the power you were using? You cannot take speed from his ass.
3) When Goku arrives, what level of power is he using now? The power he used at the blast, the power he used to outspeed Vegeta or his initial power?
Tough question. I think he's likely to be using the same level he used against Vegeta, at least from my POV:
Freeza (warm up) >= Goku (warm up) >> Freeza (tooling Vegeta) >> Freeza (initial) >= Vegeta
4) When he decides to get serious, do you think this power trumps everything else seen before hand?
I think it likely does. But do you think Freeza (kicking Vegeta's blast) = Freeza (non hands), right?
Show me how you see it numerically, please.