Dont use anything on your face. just use a light moisturizer and apply it only on the verrrry dry spots if something becomes raw. and just use a light cleanser like cerave hydrating cleanser and get like carmex or something for the lips.
I would stop the soda too (if you drink it) or anything sugary- coffee, tea, etc. drink water (and not just 5 cups a day which is total bull) just when you wake up and into breakfast one should drink 1000ML. And with this you pay have to use the toliet more than usual but drinking a lot of water will make you feel better overall. Get like a camelbak water bottle with the clearly marked amounts on the side so you know how much you are consuming daily.
My brother and i both didnt have hair loss issues whilst on the medication- but what i think you should do is just tweak your hair care a bit. Like if you normally shampoo and condition everyday (which on the meds could damage your hair from the loss of oil)- instead condition everyday but only shampoo 1 or 2 times a week.
Lastly its so odd, i never had a fatty meal with my meds ( im guessing something high in fat would be like milk, yogurt, or peanut butter?) Im lactose intolerant and also allergic to soy and almonds. I never thought i was lactose intolerant in till i got tested and found that the stomach issues was because of it, and also when i stopped drinking milk, yogurt, ice cream my breakouts decreased. It was sad that i couldnt have ice cream at the end of the day but i found something to replace it that im happy about i make a green shake in my blender. 1 cup of water, 4 or 5 ice cubes, 2 big hand fulls of spinach, a banana, and if im feeling a bit in need of sugar i will throw in a spoon full of raw sugar and mix it up. idk why but i like it a lot and it doesnt have dairy! easy way to eat veggies!
Anyways i went on a whirl- good luck! 
Did your derm tell you how much fat you need to eat with your meal?
There are three basic/general things you can do to prevent relapse: take a higher dose or a maintenance dose, be sure to eat a lot of fat, and go on a topical maintenance if needed.
I don't know how to prevent joint problems other than taking a lower dose, but you could use minoxidil to prevent hair loss.
It's best to talk to your derm, of course!
I just went on accutane and here is what I do. I know the medication is working really well because I am already over the initial breakout stage and I am experiencing lots of the side effects.
Cleanse. Morning and night. I use Liz Earle Cleansing Polish with a rag type thing that helps wipe away dry skin.
Moisturize. Morning and night. I use Embryolisse 24 Hour Miracle Cream. It really works wonders.
As to the fatty meals, I am a vegan but still I incorporate lots of fat with each pill I take. It can be a drag to make sure every meal you eat has lots of fats, but it is easy to manage after a while. Here is a list:
Peanut Butter
Chia Seeds
Nuts like walnuts, pecans, cashews, etc...
Avocados
Chips
Cheese
Bread
Most of the time I take a few of the items listed above and eat them all in one meal.
As to hair loss, I sometimes wash it daily because I tend to work out daily. I use Selsun Blue products. The moisturizing one and the medicated one. It helps with the itchiness and dryness of the scalp. I also use a hair oil during the day and at night I apply argan oil or coconut oil all over my scalp and hair. Works great for minimizing the itchiness.
As for joint pain, don't work out all the time. I just learned that this week after I could barely bend over or lie flat on my back in my bed.