If you want to be a good breeder then the sensible thing to do is to look at all your options, which you are doing, which is great. Looking at your options does not mean doing them all, and certainly does not mean doing them now. Primarily your concenr should be with the three you have. You are intelligent enough to know that bonding doesn't always work, especially when both rabbits are, or will be, hormonal, and so ideally you need to house her separately, which will mean 4 cages (one for each other girls, and one for your boy), so if that is not an option then it would be irresponsible to look for more buns when your current buns are kept in less than ideal circumstances. If you want a nethie why not discuss it with Jane (?) or whoever it was that you contacted because she will be able to give you the best advice. If you want one just as a pet then you can afford to wait until you are in a better position to give them all more appropriate care.
On a side note, most of my buns (13 out of the 14 of mine) are nethies (although most don;t look like it, they are throwbacks) and they are a lovely breed. Just don't jump into anything and find yourself overwhelmed. The mature thing to do is to learn as much as you can, and to wait until your circumstances are better.