Unfortunately the only way to get the cheats is to get the good ends with every dateable character, each having their own specific ones. I was in the same predicament as both of you, close to getting a bad end, but I didn't finish it and replayed the game. In my more recent playthroughs I have a technique to focus more on Haato's VA skills rather than the boys themselves, if you don't know how to raise specific stats, go to the VA school and talk to the boy in cat ears. He is the receptionist for extra classes! For different traits go to the book store or go to the restaraunt for food. If you want to get any sex toys, raise your knowledge to genius by reading books at the book store or going to the Agency. Want to raise affection to indifferent, caring, affectioante, or saint? Donate to the shrine! Want to raise Charm? Work at the store as a part-time job or look in Haato's mirror. Want a pet? Talk to the blonde priest and she will ask you to feed all the strays (you of course have to visit the store to get dog and cat food). The dog is very useful! If reduses stress to zero! Speaking of stress keep a keen eye on it, if it goes above 50 Haato will start spending his money for some fun and lose some stress, its especially bad near being close to his rent payment date. MOST IMPORTANTLY save before each audition so if you fail (or are like me being a perfectionst) you can reload and fix up whatever mistakes you've made. If you have anymore questions I'm sure I can give more assistance. Hopefully Meyaoi doesn't mind me giving some tips.
I know all those things you've listed. I've finished one route already. It's just boring to do the same thing every time with only a little bit of help instead of having all cheats available. I'm playing another route with full voice acting skills and it's still a chore. I just wish someone would share 100% save file.