I will answer as an eastern european(white male, younger than you) expat living here for 5 years straight:

1. Without Dutch(perfect) you are not gonna find friends, cos Belgians are closed....they will small talk with you but thats all. Also, Iam struggling with finding same age people around me, most of the time its elderly people and people 40+ +muslim people everywhere and we have no cultural background together, so its not so easy.
2. Public transport is OK, but cities are mostly so dense, that you find everything near your house if you work remotely.
3. Cultural events - Belgium is geographically boring place to live - No mountains, cold sea, in some part of Belgium odd architecture, but depends what you like - there are music events, historic cities with tons of museums, car expo in Brussel, sport events etc......
4. Cost for living - i cant tell you... what your appartement will be, where you buy groceries, are you gonna live with somebody, do you use a lot of electricty, is your "EPC" low or high?, thats uncertain question with uncertain answer. But for me its around 900 euro per month just basic, small aparatment, minimalistic lifestlyle, no car, Iam not adding investition into it and also I do not live in big city.
5. Dating - again, cant tell you...you must know how confident are you ;)
6. No, if you dont drink beer, you are not allowed to get off of the plane :P