Well done, Justme, that is another big step taken!
Like Gordon said, those chords as you played them sounded familiar to me, so you are on the path to record the song in due course.
In terms of amp tones, I guess everybody who listens will have an opinion and offer suggestions. My 2cs worth, you don't need to spend any more time knob-twiddling. I think the tone sounded good as you have it and ideal for strumming songs using the open chords that you are learning.
I say "need", cause of course exploring tones and the amp's capabilities has its own value and enjoyment, but many report spending more time in this pursuit than practicing and playing songs, which I think needs more attention in the beginning.
From a levels perspective, yes the final level of the audio file rendered/exported/bounced (whatever word you have come across) from Cubase was low. To add to Keith's comments:
When you set the recording level on the track in Cubase I imagine you can set a control to increase the gain/level as you are recording. I know how to do this in a typical DAW when using an Audio Interface but no idea how you'd do this when recording direct from the amp.
I expect that the amp settings will influence this. I also assume that you can hear what you are playing from the amp while the signal is also being routed to the PC for recording in Cubase. I may be wrong, as I say, I've never done this sort of thing. If that is the case then you need to have the amp master volume at an appropriate level.
When you look at the meters in Cubase as you are playing with the amp set appropriately, then I would learn how to get those levels averaging between -18dB to -12dB, peaking is fine but should not peak above 0dB as an absolutely and ideally perhaps not above -6dB to -3dB. Notice on this scale that things are louder as you approach 0dB. I assume that you will be seeing these meters in an obvious way in Cubase but have never used Cubase.
If when you are playing, the levels are a lot lower then you need to learn how to boost those levels as you record. As I said no idea how to do this in Cubase recording direct from an amp. But I expect a good Google will yield tutorials that provide the answer. You can also do it the old-fashioned way and read the User Manual. I expect early on in sections explaining the basics you will learn what you need to know.
That's a lot to digest, so won't go any further than that for now. I think if you figure out the above and can record from your amp at those levels you are good to go.
If on the other hand you look into your recording and find the recorded levels are fine then we can revisit this and talk more about how to get a good final level when you render from Cubase by working more on the Master track.
All that aside, well done again on recording and sharing!!