"I've been working on the chromatisation exercises and feel that my ability to stretch distance between my fretting index and middle finger is limited.  Is there a way to rectify this?"

This tutorial has exercises to build finger strength & dexterity.

Trill Drills
https://www.guitartricks.com/tutorial/1829

This one focuses on the pinky but will help the other fingers as well.

Building Pinky Strength & Dexterity
https://www.guitartricks.com/tutorial/1292

"I also notice when working on the spider exercises on the first 4 frests my index finger slides all around the fret space and doesnt sit still."

That's not necessarily bad.  Sometimes you have to let go of the lower frets to play higher frets more effectively.  But you want to aim for fretting each note cleanly & clearly when it needs to sound.  And work toward using the least amount of pressure & tension as necessary.  More is wasted effort & hinders your ability to get to the next note effectively

"When he plays the Em7 chord all his fingers are straght, mine all lean like tress in a bad wind (toward the nut) how can I rectify this?"

Building finger strength & dexterity, making a conscious effort to do it until it becomes second nature.  And a whole lot of repetitious practice.  Hope that helps!