This is much more likely due to the fact that he is now 8 months old and you only just castrated now -- you are seeing typical behaviour that starts around 8-9 months as they reach sexual maturity. It takes up to 8 weeks for the testosterone to leave their system -- what you are seeing is normal behaviour for an intact male of his age already going into adolescence and a week won't have made much difference in his testosterone levels (in other words, he'd be doing exactly this if you hadn't neutered, too). The behaviour issues (except the spraying) are definitely tied to his age and not castration. This is the age when they start to become challenging (like their teenage years!). That's why it is always good, if possible, to get puppies into formal rewards-based obedience at about 4-6 months to lay down a basis for attentive and responsive behaviour and self control while they are less rebellious, and then you can work on that base as they get older.
If you haven't done obedience I'd sure recommend it now; if you have, this is the time to work with him and keep him busy and active. Also he is exactly the age when a lot of dogs start barking -- the world is a lot more interesting to him now and he has his adult voice and he wants to use it when he gets excited. Jaspar was around the same age when he started barking for attention, for example (something he still likes to do as anyone who was at the agility this weekend willhave seen!!). Many puppies are very quiet until they hit adolescence.
If you don't have a good book on the stages puppies go through and managing and training puppies, I'd recommend getting something like any of Dr Ian Dunbar's books on raising puppies (available from Amazon in the UK).
The spraying is a consequence of his reaching a certain point in sexual maturity and is probably strongly influenced by the fact that he wasn't neutered at a slightly younger age -- he's spraying (marking) because he is full of testosterone and his body is telling him this is what he needs to do -- he'd already reached that sexual tipping point for this behaviour to come to the fore. A lot of vets recommend neutering a bit earlier before the spraying ever starts -- at about 6-7 months -- that is a better guarantee that they won't start and continue to do it afterwards. If they have already started, there's a somewhat lower chance that neutering will help in the spraying department. Spraying is a behaviour to train away from anyway.
Even neutered males will often mark inside a house they don;t know, for example, thiugh this is a lot rarer than intact males -- my experince with rescues is EVERY intact male marks inside a strage house -- that house being MINE! :yikes