Stretching only parts of a complex image to a shape

Hi,

I know the basics of Illustrator but I'm no expert so I was looking for some basic advice on how to manipulate an image to wrap around a shape.

I have an octopus design with tentacles that sits in an oblong shape when viewed normally. I am trying to apply the image to a triangle shape, so I want to stretch the top tentacles upwards and then the bottom corners out and down to the corners of the two lower triangle corners.

I understand how to transform in Photoshop (warp, perspective etc) but using these affects the whole shape. I am assuming that there must be a way of breaking the design up into smaller parts so that I only affect the areas I want to stretch, something like lots of anchor points which I can then select independently.

I can Image Trace and then expand but because the image is complex in colour the image trace loses definition and creates thousands of independent parts. All I'm looking to do is create lots of anchor points of the outline.

Anyone understand what I am trying to achieve and how I can do this easily?

Thanks in advance.