Possibly it depends on how compacted the sand is. if it is to loose it will fail.
This is a pretty solid post but it would probably depend on temperature & frost depth
I use deck screws with the project that it was used for
I used one of these to support a 4x4 post with 2 hanging plants and 2 feeders on a 6 1/2 ft post - it's super solid. I'd say you should be fine with the taller post - as long as the weight is somewhat balanced and you soil is firm. I did have a bit harder time getting this into the ground than expected, but that was mostly due to rocks, so some spade work was required.
It is a one piece device. Recommend you use top quality 2" star drive or Torx drive deck screws, not lag bolts. Do not use galvanized sheetrock screws. Not enough strength or durability.
I only used it for a mailbox post, & because of numerous (understatement) big roots i also surrounded the exposed part of the anchor with concrete to further stabilize it. I'd defer the proper answer for such a structure to the manufacturer & their specs/recommendations for durability & safety's sake. Sorry i couldnt help more.
I dont know if you are supposed to, but i surrounded the exposed part with concrete - i couldnt hammer it completely in the ground without it twisting & being out of vertical because of all the tree roots.
Yes. You only drive the tip into the ground.
If you have a 4x4 x 4' long wood post added to it.. it should be ok.. it will hold the post up right and hold the chain. I used 3" long screws (qty4 to hold post to Steel anchor
I used long deck screws