Please download the PDF file MN 148 Six By Six – Chachakkasutta to have a better understanding of the attā and anattā used in the sutta.
QUESTION: “Contact” seems to have a negative connotation something like being the source of a lot of trouble ?
The “contact” here is just the plain meaning of the meeting of the three which are “the eye”, “the sights”, and “the eye consciousness” which is called contact, and so on for the rest of the five senses.
QUESTION: what can we extract of useful for PRACTICE, from “WITH FEELING/SENSATION (VEDANA) AS A REQUISITE CONDITION THERE IS CRAVING”.” ?
In this part, the “contact” which when sense input is being used as “āyatana” instead of “indriya” (see Indriya and Āyatana – Big Difference), then the “contact” becomes samphassa (contact with defilement [san added]) and would be an akusala thought giving rise to the “feeling as requisite condition there is craving”.
So with Anapanasati or Satipatthana mindfulness one will be able to stop the progression of this bad thought and not ending with bad kamma.
QUESTION : And so on relatively to forms, consciousness, the aggregates…etc; meaning that which arises and falls away can never be considered as the “Self” ? And if so – why ? Or in other words one might also envisage a Self which is unceasing metamorphosis ?
For this question, the meaning of attā and anattā is clearly incorrect in the sense of “self” or “not self” but should be “in-control” or “not in-control“.
Read the sutta that you have downloaded at the above link, and it should be clear for the meaning of attā and anattā.
With metta.