Putting up cameras isn't going to make anything better. If anything, it could make the situation worse because the neighbour who put them up could interpret it as "oh, so the war is on, is it?" and this could cause the situation to escalate to unimaginable levels where people could start getting injured.

An approach to consider is to complain to management that the cameras are an invasion of the privacy that you rent from them. By allowing cameras to record you in the yard that you are also renting, your reasonable expectation of privacy is no longer being met. Demand that they remove the cameras so that you can continue to enjoy privacy.

Regarding the dogs, if your rental agreement doesn't allow you to have pets then they are discriminating against you. If they've changed the agreement, then they are being unfair, and compensation may be required (e.g., to pay for moving expenses, time for lost sleep, etc.). If the dogs wake you from your sleep, then the facility you are renting is no longer of the same quality it was when you rented in the past.

Regarding the lock on the gate, the landlord must remove that because it wasn't there before, and it may also be creating a safety hazard since your ability to leave the premises in the event of an emergency (e.g., fire, earthquake, etc.) is now being impeded.

You should also talk to the local tenant/rental authorities. If you don't know how to contact them, or which department it is, then contact your local city hall and ask them who you should speak to. They will know the rental/tenancy laws and will be able to provide you with some direction on how to get this problem resolved.

Remember: It is not up to you to resolve this directly with your neighbour, rather it is up to your landlord to get it resolved. Why? Because the rental agreement you have is with your landlord, and not with your neighbour.

First, I don't think that I would be worried about doing things "respectively" since this jerk is clearly not someone that "RESPECTS" ANYONE! The first thing you should do is put up your own cameras, (preferably, NOT letting him know!), notify management that if they do not do something about this, you will have to seek legal council about the matter to find out what your "rights" are. If they threaten to evict you, hire a lawyer and sue them for not providing proper security for your home from idiots like this!!!! You can find cameras on EBAY or elsewhere pretty cheap. The smaller the camera the better so as he doesn't detect the camera. Put them inside your home facing a window and just record what goes on each day. You can also buy motion detector cameras that only record when there is movement. AND, you can always get bolt cutters and cut the lock EVERYTIME he puts one on! Bullies like this are grade A JERKS and the only way to beat them is think the same way they do! (This is probably the hard part because trying to think like these idiots is almost impossible because they basically "Can't Understand Normal Things!!!!") Good Luck and DO NOT let them get away with it!