It sounds like you're both doing it about right - he's trying to avoid over discussing it with you (despite it probably being the biggest thing in his life right now), and you're trying to listen without getting too involved.
Just tell him that you're happy to listen, and that you'll give advice if he asks for it, but equally you don't want it to become the dynamic of your relationship and all consuming. Take things steady and don't get too committed to quickly. Have a think about how things will work between you if he does get 50/50 of his children? Could possibly make future cohabiting with him unfeasible.
Ignore all the above posts about leaving him because he has 'baggage'. In that case, the same would be true for every single mother too, but would you advise a man never to date a woman just because she has the 'baggage' of children? And there's nothing wrong with 50/50 shared care, as long as both parents are co operative and put the children first (many aren't, especially the ones who think they should have the kids most of the time). Every other weekend is not enough contact for a child to have a healthy relationship with that parent.
I was seeing someone ages ago, at the same time as my ex was causing drama, so it would come up in conversation quite regularly, and we'd both be quite comfortable discussing it. Despite which, I was managing the problem comfortably by myself - I wasn't looking for shoulder to cry on, I knew how I wanted to handle the issue. But the person I was seeing was very outspoken and constantly telling me my approach was completely wrong and how I should be tackling it. We had such very different ideas - mine being more tact and diplomacy, playing the long game, theirs being out and out confrontation and ultimatums. We'd end up arguing over it regularly, just being so polar opposite in that personality aspect, despite appearing to be a very similar/compatible in others.
Ironically, whenever they had problems of their own that we discussed, it nearly always appeared to be something caused (or worsened) by their own confrontational and unreasonable nature. Of course I did the diplomatic thing and bit my tongue rather than give my honest opinion when I didn't agree with them.
By contrast, with my current partner, we can openly discuss anything, and we both give and respect each other's opinions. But then we just seem to be on the same wavelength so we're usually thinking along similar lines anyway.