score:3
You say that your passport is considered weak. Usually what this means is that people from your country are believed (rightly or otherwise) to be more likely to overstay a visit, and by showing that you have traveled to "stronger" countries and left on time helps to overcome this presumption. Your European travel history will likely serve this purpose.
Given this, it may in fact be to your credit that you have an expired, unused Singaporean visa in your passport. That you cancelled your earlier trip due to the pandemic shows that you are not desperate to go to Singapore, which can only help your case in all but the most degenerate situations.
Perhaps if you had three or four unexplained unused visas, that might call into question your credibility, but with a single unused visa and a good explanation, there should be no issue.