I think relatives often have forgotten how little routine you can have in the early months especially when breastfeeding. Bottle fed babies are much easier to put into a routine as you know exactly how much they drink. Also, nobody really understands what it's like to have a difficult baby until they have one or live with one. My mum didn't really understand for example until I stayed with my parents for two weeks and they were shocked at how hard it was with a baby like mine.
The sleep window is probably your best bet for now if like I had your baby doesn't seem to have a routine. If you're struggling with trading tiredness signs, try using Huckleberry phone app (it's free). Based on your child's age, number of naps per day etc. they give you an optimal sleep sweet spot predictor and it's been mostly very accurate for us. The rule of thumb seems to be the more the baby sleep the better sleep gets, and it was certainly true for us.
As for crying, on one end of the spectrum there is shutting the room on your child and leaving there no matter how many hours they cry, and attachment parenting taken to a level where you sleep with your child and carry them and feed them so that they never cry until they are 2, 3 or even 4 years old.
There is also waiting a few minutes to see if your child will settle or at least calm a bit, and going back to them if you think they won't. That's what I did and eventually she learnt to self soothe. It's a slow process and not for everybody and having read all the main studies (I have a research background in the biological sciences) nobody has been able to demonstrate if and what level of crying is detrimental, although as of this morning a study by Warwick University on just this topic (not read the actual paper yet) showed that actually they could not find any evidence of developmental problems in 18 month olds that were left to cry at times from birth up until then and that overall they cried less at 18 months. Of course when a baby cries their cortisol goes up. That's a normal response to stress and we learn to self regulate as children.
In my view, we have a much happier child than before and I'm a lot happier too. A mum with PND isn't going to find parenting much fun to their child's detriment. A child who doesn't have the opportunity to learn to self regulate and is always placated by eg the breast or food until they are toddlers or even older may end up associating confort with food which is something that personally worried me. Also, I'm sure when women had 7 children they had to leave them to cry a little sometimes as they had their hands too full!
If you love your child and look after them well, they will be securely attached to you.
Big hug - and hang in there!