Hey again @Tom_Tom
So OK, got to listen to the new version
In my case, I prefer to raise the volume knob than to have to quickly put everything down, so the levels are better and I think this mix has gained some clarity. I was able to crank up the volume knob quite hard and didn't get too much unwanted distortion during playback. I find the low end more pleasant now, the kick for example got rid of that extra "thump" low-end that was sucking a lot of dynamic out of the track in the previous version, now it sounds more short and let other transients coming through. I prefer this, that's what I mean by clarity, you can now here more elements if you pay attention, the kick was masking some of them before I think.
But maybe people will prefer the previous loudest version, it's often the case, make the test around you if you can and get people to do some A/B listening or leave the tracks on SndCld & compare the likes.
So now of course with this new version, you now have lower levels and some headroom to play with. You could try to raise the all mix or push it a bit harder with a limiter if you want to compete with a "commercial" track but it's the point where things are getting difficult, also the point where you could ruin any track.
The story behind this ( since the beginning ) is that YES : it's a very difficult task to try to master your track yourself and it will give you some hard time and even bring disappointment along the way. That's why many artist don't push themselves into this area and hang over their mixes to audio engineers. So yea, definitely a critical and hard step in the process that involves a lot of work & practice before you'll feel confident about doing it, but don't make yourself crazy with a perfect master as a goal to reach
Do not expect any of the online mastering platforms to give you a magical & perfect result and to replace an audio engineer work on your mix, there's no any advanced AI science or best in the world algorithm to replace that.
Those tools can help to re-balanced a mix, in terms of tonal balance and levels and help you to make the track sit in a defined headroom & overall level range but they won't do magical voodoo You can use them to kind of "normalize" an already well balanced mix with for example 6dBFS of headroom in mind, or you could perhaps benefit of some algorithm correction when targeting specific outputs levels such as online distribution like YT, Tidal, Spotify...ect. And again, your mix have to be already sounding good before. I don't believe in using extreme settings and push a mix down to a master level track using those online platforms, it has to be done through incremental steps along the process IMHO.
Next to that, keep in mind that it's all starting with how your mix-down sounds in the end, it's really the key, and the most you've been able to achieve during mix-down, the less tedious the track should be to master.
So before even thinking to final master a track, you have to be happy with your mixing work and the same principle applies for those online mixing/mastering services : if what you upload on there is not already good, it won't make magic.
I won't dive into the melody & arrangement too much here, but @kuchenchef raised some good points in his comments. The only thing I would say in general about melody, arrangement & sounds is that if the track has got something appealing, it would work, even if the mastering isn't perfect, because that's the first essence of music : to catch people brain's & souls and getting them to be hooked by a sound, a chord, a rhythm...
Take all of this easy, don't push yourself too hard on one track to get it perfect, that's where you'll have a good chance to ruin your efforts, take breaks and learn at your own pace, don't expect to have it sound perfect in first place and keep the creative side of music making separated from the technical one. It takes time to get there and along the way you need to keep the fun & passion of doing it & learning.
It's a good idea to keep a copy of your work while your progressing to be able to A/B when you started and what you've done a few month, years after. Many people will through complete mixes into the trash because they are not happy with them but if you're not referencing your own progress it can sometime be an endless cycle.
Sorry for the long writing & hope you found something useful in the comments