No April. He used to write in upper and lower case. It is since he has been in prison that he has written in captitals. Probably to make it easier for the censors to read his letters before they went out. So he doesn't say things like "And don't forget the two sticks of dynamite in your next food parcel".
No this is not true, I have seen this before in the diagram of farm he drew for police on morning of massacre. OK maybe a bit emotional at the time and can be forgiven for this but I have seen capitals and mis-spelling before, maybe even as bad as me.