I'm actually almost eight weeks with my little cockatiel babies. I'm no professional, but will give any knowledge I obtained from raising mine.
1) I saw that you may bathe it around five weeks, however, most pages suggest a gentle mist as their immune system may not handle a full on bath. We started to mist them around five weeks.
2) I actually used KAYTEE it is designed for baby birds including cockatiels. I would recommend it and as a person who purchases based off of reviews, it seemed to be recommended a lot by others as well. As Barry Collins stated, the act of giving the food is very dangerous and there are risks to it. Personally, I just watched youtube videos to see how it should look like and read on the topic and the risks to it.
3) Weaning should be 8-12 weeks as Barry said. I offered my babies food around 5 weeks mostly so they know what it is and try on their own to learn. Around this time they would pick up the seed and play with it in their mouth, but it would ultimately fall out. However, around the sixth week they began eating, but still needed hand feeding and their parents. I bought a smaller seed meant for canaries as I read that it could be easier for growing birds to eat then as they grow start to give them regular food, but I'm not sure if it made a difference. (However, my birds only ate when the food was scattered on the floor or in a small container). Around 7 weeks they began eating fairly decently. *Some sites did recommend giving them millet as a way around five weeks I guess this plays with the idea of the smaller seed*
4) Gender is what I'm having trouble with as different people think different genders for my birds. There are tests you could do varying on feather, blood, or eggshell. This is a linkI recently saw on this site, but on another forum.
Animal Genetics | Genetic Testing Services . Blood is about 20, feather and eggshell 25.
Avianbiotech.com - Avian Sexing Center this is the page for more information on each test. There are ways to tell gender visually (may not be accurate) but it works. Physically one could tell by their feathers or by their behavior; feathers I'd recommend looking up your type of bird or if you have no clue you could lookup cockatiels and their mutation and see or ask this site as many people could help.
5)It is recommended that you begin to touch the little ones even if not and feeding fairly early. Mine got accustomed to me and my family through this, however, if your bird is scared you could start from slowly putting your hand into the cage to pet him/her, or let him out to fly and to explore his location (if they can), also don't constantly be with them and let them relax to become less nervous then go in.
As Barry said I also would love to see some pictures and would be curious to know the answers to his questions. Hope I helped it's all from my first-time experience.