Lets take it slowly.
3) Hajj, Ramadan etc are essential parts of Islam but these are rejected outright in Gurmat. This in fact shows that Islam is not the way to reach Waheguru according to Sikhi. The page you talk about is two things:
3.1. We all know that once we learn things it is difficult to de-learn. So the Gurus always spoke in metaphors and also used vocabulary of the persons to explain them. When talking to farmers they explained in agricultural terms (the field became the human body, seeds were good actions and it was watered with Naam - this Shabad can be found on panna 23, SGGS). Besides that several religious concepts of other religions were redefined to explain them. Hindu term Jati means celibacy but in Gurbani it became living the life of a householder BUT in the same time having self control (over your senses). Exactly in the same way, the Gurus saw that there were people reciting 5 Namaz but yet indulging in immoral activities, in a way these 5 prayers proved to be futile. Guru ji then said why not replace these prayers with virtues, atleast they will make you a better person instead of parroting verses over and over again without becoming a better person. Those tuks are Islam Namaz redefined and not an encouragement to recite prayers 5 times.
3.2. Several lines have been misstranslated there. 'Prophet Muhammad' is nowhere mentioned in the Gurmukhi but appears in the English translation somehow.
4) Theres two things there, the Bhagats belonged to either Hinduism or Islam and secondly they lived when Sikhi did not exist yet.
4.1. Lets take one at a time. Was Bhagat Naamdev Ji really a Hindu? Lets see his writings for that, Panna 875 of SGGS is of importance to this discussion:
O Pandit, I saw your Raam Chand coming too; he lost his wife, fighting a war against Raawan. ||3|| The Hindu is sightless; the Muslim has only one eye. The Gyani is wiser than both of them. The Hindu worships at the temple, the Muslim at the mosque. Naam Dev serves that Lord, who is not limited to either the temple or the mosque.
He may have been born in a Hindu household, much like Guru Nanak Dev Ji, but those lines clearly show he rejected Hinduism.
4.2. Did he really live before Sikhi existed? Thats a misconception created by some historians who did not know where to place the Bhagats exactly, so their date of births are usually messed. If the Bhagats lived before Sikhi then they could not have written in Gurmukhi and there is no guarantee that there writings were not corrupted by the time the Gurus came. Others than that, the language of the Bhagats show influence of the Gurus with words such as Gurmat being used often.
Now there are also historical proofs that the Bhagats were contemponaries of the Gurus and met Guru Ji. One such Gurdwara exists in a town called Ayodhya (where several Bhagats met Guru Nanak Dev Ji).
The nephew of Guru Arjan Dev Ji also wrote a Janamsakhi which confirms that Bhagats (Bhagat Naamdev is mentioned) went to meet Guru Nanak Sahib on Wahegurus Hukam.
This will take some time to grasp because alot of misconceptions do exist and its much different to what is often said or written... I also used to believe the things you stated for years until I delved even deeper into Sikhi.
