Pizza Boy and RetroArch should work too.
Since the game is turn based and mostly menu driven, it plays well on phones and tablets.
You can always grind a couple of levels the day before the boss fight. 9th dungeon floor is the one that should give the most experience. Try to get old porn cards at the minigame after battles to get more experience, but apart from that the grinding is as it is, sorry xD
Here's a video of the boss fight at level 11 (it should be quite easier level 12): https://files.catbox.moe/4ddfme.webm
Colorao's 2nd battle strategy: