Hello and welcome to BW forums
Wow! You are doing brilliantly!!
Honestly, I realise it might not feel like it when your LO is short napping and waking in the night and you are just exhausted from it all but I can see SO many great achievements in your descriptions of what is happening and where you are up to! Seriously, you need to give yourself (and the other care givers) credit for how far you have come and what's been achieved.
First of all, those early weeks which might have seemed like he was easier to get to sleep or keep asleep, well that's the sleepy phase and new borns do tend to sleep a great deal. What you've described starting a couple of weeks back, harder to keep asleep, that is him coming out of his new born sleepy phase and starting to be a bit more of of a "baby" rather than a new born, if that makes sense. Things do change at that point - but don't panic about having done something wrong, you're doing everything right!!
But I'm still unable to find a solution to my LO's sleeping issues
There's one thing that I notice with BW. It can sound like every issue can be solved in a breeze but many of us don't take enough notice of the chapter in Tracy's book where she says EASY is not easy. it takes time, effort and patience. Sleep training is a gradual process and isn't achieved over night but rather as an on-going learning process, LO learns from you and you learn from LO, it's team work really and at 2 months you are still learning who your LO is, you really can't expect to "know" him inside out just yet.
but now this frustration is making me look for the easier way out just to make him sleep
I think you can ask yourself here, what IS the easier way out? If there is one can you incorporate it into your daily routine to give you a bit of a break but also treat LO with respect and gently teach him to self settle and nap well?
The only time he sleeps 1.5-2h is in his pram if we go for a walk in the park for his first nap
Perhaps this? Personally I see no problem with doing a pram nap. My LO was one who refused to sleep in his pram and I even had a thread here asking if I should re-sleep-train into the pram to make life a bit easier to get out and about! Babies form habits per nap, they like predictable routine, so if you go out daily for the first nap and this is sustainable for a while then honestly I would just keep on doing this. You could, if you wanted, aim to get him to sleep in the pram when *not* moving or with just a little push back and forth which in my opinion would be preferable because come a day you don't want to go out, it's raining, or you don't feel 100% you could then pram nap in the house just doing a bit of rocking rather than feeling you had no option at all but to leave the house. Props are things which help baby sleep but which the parent has to do to make it happen, it's something we can end up feeling "trapped" in but firstly we can use that to our advantage (always going out for the first nap means you always get a walk and fresh air which is a great way to feel better in yourself, or LO may be more "portable" meaning you are more able to get to baby groups, a cafe, etc) and secondly sometimes those props are just helpful to us for a time and when they are no longer helpful we can decide to drop it (accepting that you need to break the habit which takes some effort but not impossible).
During the day he suffers the 40 min.nap intruder and can't transition into the next cycle. I have tried the W2S, putting my hands to prevent jolts, leaving him in the crib - but nothing seems to work the first few times and he always wakes up. Putting him back to sleep = mission impossible. Do you think I should choose only one method and stick with it for a while longer?
All these things are helpful. If he wakes and is calling for you then you wouldn't leave him in the crib without responding but if he wakes and just lays there calmly then yes leave him and he might go back to sleep. W2S and HTTJ (holding through the jolts) are helpful but if they are driving you insane give yourself a break. This is a time when your LO is learning and it's going to take practise.
But we all put him awake in his crib and he falls asleep there, swaddled with a hand on his shoulder/arm, sometimes with shush/pat.
This is super!! Just look at how young he is and he is able to fall asleep in his crib!
Most of the time we leave him in his crib and he falls back asleep on his own, for another 40 min.
This is super!! Honestly this is a huge huge step ion the right direction. This shows that your efforts are helping him to feel relaxed and confident to go back to sleep without needing to be rocked or patted at every single wake up. Every time he does this it is an achievement.
but wakes up every 3-4 hours for a feed. Although I dont think he eats much - he only takes one breast - while during the day he usually feeds on both for 15 min.each. Although I think he eats well during the day, I thought about upping his feeds with a bottle of EBM, but I'm afraid I might create some kind of dependence on the bottle and problems with breastfeeding. I was expecting that he would go longer stretches during nighttime than daytime, especially since he's quite a big baby (6 kg). Will that eventually happen or should I do something to elimimate night feeds? I used to do cluster feeding, now I only give him DF - a bottle od EBM between 10 and 11, depending when he goes to bed. The amount he drinks varies between 4 and 6 ounces.
I would post this on the BF board. I'm not great with BF advice but I would say that topping up with a bottle of EBM might not be the way forward, if he needs more at each feed then you need your supply to increase and the way to do that is for him to nurse. Nursing at night, I believe, is particularly helpful for increasing supply to his need. Feeding every 3-4hrs is perfect at night. It will gradually increase naturally to where you get one longer stretch of sleep, 5hrs is classed as sleeping through, so a stretch of 4hrs is great, well on the way. You would expect to see just one longer stretch, doing 4hrs between two feeds doesn't mean you can expect every feed to extend to that length yet. Give it time.
Please do feel welcome to post to the BF board for much more experienced support.
Hope something here is helpful. I really do think you've made fantastic progress already.