Can he call non-Muslims to Islam with the little knowledge that he has?

There is nothing at all wrong with conveying what you know of the
religion of Allaah to non-Muslims, as long as you are certain that it is correct, such as
the basics that you mention, like the five pillars of Islam or the pillars of eemaan
(faith). Indeed, this is probably obligatory upon you, as Allaah says (interpretation of
the meaning): “Let there arise out of you a group of people inviting to all that
is good (Islam), enjoining al-ma’roof (i.e., Islamic monotheism and all that Islam
orders one to do) and forbidding al-munkar (polytheism and disbelief and all that Islam
has forbidden). And it is they who are the successful.” [Aal ‘Imraan 3:104]

The Prophet
(peace and blessings of Allaah be upon him) said:
“Convey from me, even an aayah.” (Reported by al-Bukhaari). Ibn Hajar (may
Allaah have mercy on him) said: He said in the hadeeth, “even an aayah”, meaning
one aayah, as if he was saying that every listener should hasten to convey whatever aayaat
he heard, even if it is only a few. Some of the Sahaabah set out to call their tribes to
Islam when they had only a little knowledge that they had gained during the brief time
they had sat with the Prophet
(peace and blessings of Allaah be upon him). But even
though their knowledge was so little, it was correct and was blessed, and because of their
sincerity, Allaah benefitted others through it. Al-Tufayl ibn ‘Umar went from Makkah
to his people Daws with the limited amount of knowledge that he had, then he came to the
Prophet
(peace and blessings of Allaah be upon him) in Madeenah accompanied by eighty
families of Daws, all of whom had become Muslim, and among whom was Abu Hurayrah (may
Allaah be pleased with him).

Know that some non-Muslims may become Muslim for the slightest reason
and by hearing the briefest word said to them. Do not think that the knowledge you have is
too little for the purposes of conveying the Message. “… invite them to your
Lord. Verily! You indeed are on the (true) straight guidance.” [al-Hajj 22:67 –
interpretation of the meaning].