Thanks! It's not from scratch mind, it's made on top of the gutted 7drl entry from last year, which itself was made on top of the year before and so on all the way back to my 2011 entry. Standing on the shoulders of a giants and all that.
I struggled with the controls myself when I first implemented it, which is why there are a few different options for controlling the blocks. I kind of think this is unavoidable though because controlling two things at once is just a bit of a mind trip. To start with it might help to just focus on fighting, and only use W to bring blocks down faster when needed. When there's no space for them to go they fill in the holes, so you don't have to worry about fitting them in just right. Then you can start bringing in manual control over time.
Some tips for fighting are to make sure you are using your bow liberally. You can place blocks over the spawners to effectively kill them. You also have a wider field of view than everything else.