I don´t
agree with you on your personal definition of "vice", for in many cases
vicious behaviour not only comprises non-moral, i.e. morally irrelevant
self-damage but also plain immorality.

Keep in mind that, as Merriam-Webster's says, "VICIOUS may directly oppose virtuous in implying moral depravity, or may connote malignancy, cruelty, or destructive violence". Thus the connotations of 'vicious' are not necessarily a good way to decide what constitutes vice.

For instance, someone excessively
smoking in public is doing harm to his health, but to other people´s health
as well, when there´s a fundamental moral duty saying that you mustn´t do
intentional harm to others.

The evil here of inflicting smoke on others is logically independent of the harm to oneself. Inflicting such harm on others without harming oneself would still be evil, but harming only oneself (e.g. by using chewing tobacco) would not.

 And  someone always being viciously late at work
is doing no harm to himself, but nonetheless his behaviour is plainly
immoral.

Here, what is evil is not the worker's sloth, but his fraud in not fulfulling his work contract.

Besides, I doubt that your Robinson couldn´t engage in immorality.
First of all, there are not only social but also individual dimensions of
morality like self-responsibility. So we could well argue out whether a man
obsessively banging his against the wall for whatever stupid reason is not
only behaving viciously but also immorally insofar as it would be his
individual moral duty not to deliberately inflict damage upon himself.

'Moral' is your word, not mine. In my book I've instead talked about 'ethics', 'evil', 'virtue', and 'vice'.  As I use the term, one cannot be unethical to oneself. I deliberately distinguish between ethics as behavior toward other beings, and virtue/vice as behavior toward oneself. I would probably define 'morality' as the union of virtue and ethics (including one's political behavior). I would say that we can legislate ethics, but not morality (i.e. not the component of morality that lies outside ethics, namely virtue/vice.)

In addition one could also blame that man for behaving socially immoral, for in
case he might suffer a brain injury the social community would have to bear
the costs of his nursing.

In economics this sort of taking advantage is called "moral hazard", and it is indeed evil.  Note that you cannot impose a moral hazard on yourself.

Secondly, even if Robinson were the only human
being on his island, he could nevertheless behave immorally. He had been
morally socialized within an ethical community before stranding on that
deserted island and so I presume that he already possesses an autonomous
conscience, in order for which to be "operational" no extraneous sanctions
by fellow men are needed.

He could have evil intentions, yes, but his actions could not be evil if the only harm he can inflict is on himself.

Furthermore, if Robinson in his solitary boredom
suddenly derived pleasure from the thought of slinging living lizards
against a coconut tree as a pastime, it could well be due to  moral
soliloquy that he eventually refrains from realizing his odd idea in spite
of feeling like doing so.

Yes, feelings of malice constitutes one of my five kinds of vice, and of course does not require action. Only when such malice leads to an intention to act does it become unethical.