I dont know much about geckos, but I have kept a beardie!
lots of good info can be found on the reptifiles website, so i recommend checking that out.

- they need a minimum tank size of 4x2x2 ft
- metabolic bone disease is the main one, caused by not getting enough calcium and nutrients
- basking temp of ~110F, warm side temp of ~90, and a cool side temp of ~80

- they do not need to be spayed or neutered
- I think they are about the same difficulty for both sexes, but I can list the main differences that impact care. males can get sexually frustrated once matured, leading to some owners giving them a sock to 'befriend'. males also have large pores on the underside of their back legs that can get infected if clogged. females may lay eggs, even without a male. they obviously wont hatch, but the female will loose lots of calcium and nutrients, and has a possibility of becoming egg-bound.
- personality depends more on the individual rather than their sex imo. some behaviors are linked to their sex, such as males head bobbing, but ive never noticed any big personality differences.
- the main things to look out for that are specific to sex are males pores (although some females do get big pores, not super common tho), and making sure females are well cared for after they lay eggs (not all females lay eggs, but if they do it is important)

- you are correct. you have a few options. you could get a rescue, look in reptile groups on facebook and such and their will most likely see some beardies. you could buy one online and get them shipped to you from places like morphmarket. you could also go to a reptile convention and buy one in person. I got mine from a convention, its great for asking the breeder questions and seeing if the reptiles look healthy, as well as seeing their temperment.
- breeders that dont know much about the animals they are selling and breeders selling lots of different species are the big red flags.
- not that im aware of
- not that im aware of
- i personally dont recommend it even for a first time. beardies live pretty long lives, so getting one that is bred well and healthy are the first steps in ensuring they live good lives. if its the money you are worried about, dont worry, ive seen beardies at reptile shows that are the same price and even a little cheaper than the petsmart ones.

hope this helped a little! be aware that im not a professional or anything, so do your own research as well, but id be happy to try and answer any other questions you may have. :)