This sounds just like my DS. He's 3 1/2 now, and I really thought we'd avoided the worst of the terrible twos as he didn't really have tantrums until he hit almost 3. It all went downhill when I was visibly pregnant and once DS2 arrived. He had reflux as a baby, and was always quick to grumble and cry, but had been a fairly sunny little toddler.
He would just resist everything, just to say no. Even things he liked (going to the park, eating his favourite food) - it was as if everything needed to be his idea, on his timetable, or he would refuse. It was exhausting. Bedtimes suddenly took hours, he'd scream and shout for seemingly no reason. We wondered if we were doing something wrong, or was he ok - and why didn't any of our friends' children seem to behave like this. He always saved the worst behaviour for us.
It has got better - I think time is mainly what he needed - and he has been absolutely lovely for the last month or so. It definitely helped to signpost everything to him multiple times - so i would tell him the night before what our plans were for the next day, then remind him throughout the day. I realised I was giving him too many choices so I reduced the number of options I was offering. I stuck to natural consequences - so if he didn't want to wear a coat outside, fine, I wouldn't argue, I would just tell him it was his choice and he would get cold. We also had absolute red lines - hitting, throwing etc.. We've tried limiting the number of warnings he gets - we realised we were trying to negotiate too much, when actually what he needed was one (or two) warnings and then take action.
Also - really importantly, lots of cuddles, hugs, telling him we loved him (even if it didn't feel like we liked him), noticing when DH was struggling with him and vice versa, making a really big fuss when he did anything positive (and sometimes you had to really search for it!).
Incidentally, we measured him for the first time in 3 months or so. He has shot up 6 centimetres, so I now suspect a serious growth spurt has played havoc also.
We are not out of the woods, and he's always been quick to anger even as a baby, but I feel like the real DS is coming back so I think you just need to be kind to yourselves, and him, and ride it out a little longer.