Thank you for the feedback! Most of these issues are known, so I will explain why they were left to come with the update.
The rendering problem happens only if your monitor has a refresh rate above 60 Hz. This is because of the game's engine and I am not sure how to exactly fix it. You could enable VSync in the settings, it should help to an extend.
The enemy spawning is known to have this problem. I have tried fixing it a couple of times, which made it more rare, but it still happens occasionally.
You have an XP bar under you HP. Also a sound is played whenever you level up as well as a little popup text appearing onto your character. There are some UI changes coming in 0.4, which will improve the ability to see these things, so it should be better then.
There will be clickable icons in the UI to access all menus with the overlay update I am doing, so entering the menus should be a bit easier.
You gain the special cards only when you experience a growth scene. You can then use e growth point to choose a skill to enhance. Also they are the same skills every time unlike the random ones you get upon level up. Keep in mind that they have a max level each, meaning you can upgrade them only 3 times.
I know what you mean by having a better environment, but as I haven't found a pixel artist who is willing to make sprites for the game, making such things is quite hard for me and as I am not a very good at arts, I do not want to ruin the look of the game with my doodles, so this will be held off for a bit until I have someone who has the skill to do it.