Thank you for your extensive review! In light of that, I'm going to attempt to address each of your points with one of my own. Apologies if it's a bit long :)
One, I have incorporated multiple controls for shooting into the game. If one doesn't work, another might. Check the description or the in-game page labeled "controls" to find out what does what :)
Two, I have begun to encounter problems with some values behaving as they should in my downloadable test version and the same values not working in the online version. The gold value is one of these values. I'll look into how to fix it, although it may take more time than fixing the HP problem that arose before the patch.
However, I am also working on an update that should phase out the need for gold to upgrade your max health. :P
Three, the pacifist achievement tree has been bugging out to some major degree, and I had planned on maybe even getting rid of that achievement all together and replacing it with some more straight forward ones. For your information, the pacifist achievement tree was supposed to activate once you dodged flies without killing them for an extensive period of time (ten minutes to be exact)... yeah, I'm probably getting rid of that.
Three, I'm glad you thought that the movement/aiming system was a good piece of gameplay. I was considering replacing it with twin stick controls, but even if I do I believe I'll release an "original mode" or something along those lines with the original controls still intact.
Finally, if you got far enough in the game, you should have unlocked a few skins in the unlocks menu. Simply click on the word "Unlocks" in the main menu and select a skin, then play the game and the skin should show up. This should help make the spider more visible :)
Good luck, and thanks for the feedback!
P. S. good job getting to the boss with the gold system glitching, on one health it took me a few days to do!