Im no super mum but I can advise you in my capacity as a nursery nurse.
Hes only 2 hes very young and wont 'get' actions and consequences thats why you need to keep reminding him,what behaviour you expect,why you expect it and how you will feel,in short sentences,ie-
Thomas in a bit,we are going to the park.
When we are there you need to hold on to the pushchair.
I need to see where you are because its dangerous.
We will have a good time at the park and I will smile and so will you,if you do what Mummy says you can have another go on the swings/packet of raisins/see Nanny.
All the way there talk about what will happen.
If he runs away Be cross be assertive say NO!!.
RE the poo smearing this could be a sign hes aware of poo and needs now to be introduced to using the loo to poo and flush away the poo.
Be confident and aware when you speak dont offer choices dont negotiate these are the rules he must stick to them.
Sounds like you are both having a very tough time.
In reply to the old ladies I would say I expect it seems a very long time ago your children were small...haha.