It's OK to mix the old substrate with the new substrate, since the old substrate is relatively fresh. (If you were rehousing after a long time, I would recommend all fresh substrate.)
Yes as long as the space between the top of the substrate and the lid does not exceed 1.5 times the tarantula's diagonal legspan.
The rule of thumb about vertical space not exceeding 1.5 times the tarantula's legspan is a maximum, not a minimum. It's to limit the risk of injury from a fall.
That looks pretty good, but I can't really visualize the depth of the substrate from that angle. How much vertical space is there, and how big is the tarantula?
His leg span is roughly 5cm, Substrate to the top is 8cm might need to add a little bit more to the enclosure, but when I got in last night he blocked his entrance off and webbed it so I'm guessing he is pre molt, substrate dried fine.
The amended enclosure is good, the height is good so there's no need to add more substrate.
Gotcha, the water is changed every single morning.
There's no need to change it every morning as long as the dish is clean and full. (I clean water dishes once a week to remove the slimy biofilm that accumulates.)
Thanks for the tips really appreciated I did do research before I bought him I promise, so many different and conflicting information. He's still inside his blocked hide hasn't come out since my last post. He has no water at the bottom as the dish is at the surface, should I just leave him as is? I'm sure if he needs water he'll break himself out the hide and look for it
Leaving them alone is usually the best approach. In time, as you get to know your spider, it will become more obvious when intervention is needed.
Now that you have found this site disregard any previous sources that you were using for tarantula care. This is your One Stop Shop and best resource.
This will be my last noob question, he is still at the bottom of the log with his hide blocked off I am 70% sure he is premolt, the water source is at the top of his hide and I'm positive he hasn't been out since everything is undisturbed, just wondering how is getting water if he is at all he isn't shown any signs of dehydration and I can't put a water source down there without breaking into the hide or disturbing him is it still best to leave him or try and get a small bottle cap of water in there?
If you're worried that he might not find his dish, you could put a second dish at the bottom of the log closer to where he is (assuming he can get out there), but I wouldn't disturb him by breaking the seal.