Don't worry about routines - follow your DS's lead - feed him when he's hungry, help get him to sleep when he's tired. More predictable naps are unlikely to develop much before 4 months, very likely later. I couldn't tell you at what time of day my 6 m.o. is likely to nap (although I know how long after waking up he will need to sleep again).
Bedtime routines are useful from around 4-6 months when babies start to be able to remember how they went to sleep the previous night. At this stage,
It definitely sounds to me as if he's overtired. At this age, my DS had to wake up from his last nap, I'd change his nappy while he cried with tiredness and he'd then feed to sleep. I tried doing a 'routine' but had the same problem as you. What I did was to sing a certain song as I did his nappy and at the start of the feed, to get him into the idea that it was bedtime. It was only around 4 months that we started adding more to it.
Many babies don't develop an early bedtime until around 3-4 months. It is tough not having your evenings, but you will get there.
It sounds like you're doing a great job - keep going, and ignore all the books which tell you what you and your baby should be doing. I'll bet your baby hasn't read any of them!
And once you are doing a 'proper' bedtime, one of you has to stay at home, or take a cot and do your routine at your friends'/families houses.I have a 6 m.o. and I've been out of the house in the evening once since he was born - and only because we took the carrycot with us to friends'. But I think that's not unusual, and I don't mind, really - all part of the new job description!