Honestly, I don't find the game very hard and I like complex gameplay systems. I just find the training to have broken elements that simply don't make sense. In the slums you can pay 1 spark at a brothel to keep your libido up and you can pay 1 spark for food at the pub each day. The elven laid will keep you clean and if you are really hurting for energy you can always use the invigorating message. I spend about 30 sparks a decade plus cleaning and food for a slave which is practically nothing especially if you have an assistant. It's easy to make a daily routine that will allow you to start each day with full energy and keep your libido up. Your attitude will flux throughout the day but it won't hurt you really.
My only issue is when you train someone, if they are too disobedient to train then you should need to instill fear either verbally or physically BEFORE training if necessary. However, I almost always find a way to improve attitude and get them training and accepting rewards which leads to us both being happy until all character progression comes grinding to a halt for no explainable reason and I have to tear down all of the progress that I made for the last 20 days to physically beat someone that is totally compliant into gaining obedience points that refuse to go up because of some quirk in the gameplay. Super annoying. If the game requires that I instill fear BEFORE training successfully then that would make sense but I just don't get what's going on. I physically forced a collar and the crown of thorns on her and I'm making her sleep on the floor naked. Her taming skill is going up but it's retarded that she was spoiled before I even bought her.
If you live in a slum, you dont get access to the dungeon, or alchemy, both of which can be useful. Not to mention that both slaver and slave would not enjoy the living conditions and thus mood will go down. As I mentioned earlier, its not necessary to suffer a routine and live cheap in a slum, those are for masochist players who really, really want a challenge. The game allows you to quickly get an apartment and a free assistant for a reason.
But of course, if you prefer to go through a routine every day, that's no prob. Just note that the food served in virgins hip is likely B+ rank so you cant rank up your slaver's endurance past that, a very key stat in this game.
As for your quips on the training sessions.
Fear makes it easy to train a slave, but it is not necessary. There are slaves that are more docile and dont need to be coerced into accepting training. Low nature slaves are one such, some others may have quirks that make them easier to train. For general purposes, most slaves need at least some fear to get anywhere, because their obedience starts off too low. Fear instills obedience, and will be replaced by devotion, awareness, habit and taming in time.
Its a common thing to have obedience fluctuate wildly around the areas D- to D+, thats because often enough the slave's awareness/taming/habit is not high enough and/or she has spoiling. Fear 3 compensates with all those, but fear slowly subsides assuming youre training them correctly i.e. not punishing/rewarding more than needed. Right now your issue here is that she has no taming and has spoil 1, whilst having fear 1. My directions in the earlier post will help with that.
Another key tip, which the game doesnt really explain. You dont HAVE to reward them all the time (although punishments are near mandatory). The game is set in such a way that past a maximum of 2 reward (on easy) will induce higher spoiling. In other words, skip some of the rewards, you dont have to give it. For me its twice a day max, no more rewards after that.
A small comment. I dont like the fact that certain slaves have spoiling before I even start, but I accept that its logical, though annoying. If youve ever had the pleasure of meeting with a real ojou-sama in real life you'll see why certain slaves seem to think the world revolves around them. Your job as slaver is to make sure they understand who is the master of this house. A few days in a cell eating dog food will cure them of their delusions of graduer (dont do this in real life, its not nice and you'll get arrested)
And lastly. This is a fairly demanding game, there's no shame in tearing down all your progress and start again. As a slave master you would eventually learn which slave is worth your time, and if they are progressing. For those that cant or wont, just chuck them and get another one. Any veteran of Jo9 would have done the same at some point.
Ive once reloaded a save after playing up to 20 days getting her to C- only to find out that her spoiling 2 is getting really annoying and I dont want to go through another 10 days getting rid of it. Nothing special. The game is harsh but fair.