Adopted cat defiling house - help!

[BAJ2011]

We have recently adopted a rescue cat - approx 18months old boy - apprently neutered. He seems very friendly, calm, great with our 15month old son...but he has done unmentionables 4 times in the 10 days we've had him, all in different places around the house. This got increasingly wearing, but last night nearly broke me - he has used our sons cot as a toilet. He peed 3 times, spraying the whole matress, all the toys and cot bars and walls. I'm getting pretty desperate now, thinking we shouldn't have got him.
Have now tried moving litter tray somewhere easier to access. Apparently they have to be shut in for 3-6 weeks to acclimatise - any opionions on this welcome! Is it something we're doing? Do we just left him out after only 2 weeks??? Help soooo needed x

this definitely sounds like stress marking as givethe said shut doors to keep him out of rooms and usually when we rehome a cat from the rescue i work at we say 2-3 weeks to keep in an adult cat, but dont let him out if hes pestering to go out let him out when hes calm and first thing in the morning and hungry so hes less liable to bolt and more liable to come home, it dosent sound like little one is upsetting him he would have picked the cot because its soft and smells neutral so he has overlaid this with his scent horrid for you but makes sense to him, have a look at his rear end you will very quickly see if he is neutered cos his pom poms will be gone if he is, and the wee dosent smell really strong like whole tom cat does