The material you've quoted ("evidence that your EEA national family member is in the UK," etc.) appears to be from the UK government's page on entering the UK as the holder of an Article 10 residence card. That doesn't apply to you, because you're seeking to enter Portugal as the holder of such a card.
The directive is somewhat ambiguous on the question of whether an Article 10 card holder should be exempt from the visa requirement when traveling without the EU/EEA family member. I think there is a way of reading it such that a visa is not required, but the current interpretation seems to be that the visa is required. I do not know whether this has ever been determined in court.
This is from Timatic, the database that your airline will use to determine whether they should let you board (emphasis added):
The following are exempt from holding a visa:
Passengers with a family member residence card issued by United Kingdom. The card must be issued to family members of a national of Switzerland or an EEA Member State . They are visa exempt for a maximum stay of 90 days and must travel with or travel to join the national of Switzerland or EEA Member State. This does not apply to passengers with a different type of residence permit.
Because you are planning to travel to Portugal without your spouse, you will therefore need a normal Schengen visa (unless you're a national of one of the visa-exempt countries; the Portuguese government has a list of countries whose nationals require visas). This is confirmed on the relevant page of VFS, the visa processing service provider:
Any applicant, travelling without his/her EEA/EU or Swiss national family member, cannot apply as EEA/EU and Swiss national family member and need to apply as Tourist, i.e. providing all the required documents and paying the applicable visa fee.
The Portuguese consulate in London has a page about visas, but that does little more than link to the VFS site.