I'm an INFJ with super strong Ti tendencies, so I can relate in a way! I thought I was an INTJ for the longest time. NOPE.

Here's how I decided: I care a lot about logic and empirical research - but ultimately, what I care about more is other people's feelings. If someone is being irrationally emotional (ie. very common), I know that me giving them logical advice might just make things worse. So even though it pains me, I just listen and validate. That is, I think first about their feelings and use them as a guide to figure out the way that I can best help them. I care more about their feelings (Fe) than about them being logical (Te).

It sounds like you have strong Ni and Si - but which is stronger? Which do you care about more? Honestly, it sounds pretty clear that you're an Ni - you think in terms of patterns and synthesis. This is shockingly hard for a lot of people and in general, iNtuitives are less common. Ni dominant is particularly rare.

That you're questioning this much and you're able to reevaluate your perspective makes me almost 100% sure you're an INFJ. Generally, ISFJs are more simple and accepting. Not to say there's anything wrong with ISFJs - they're one of my favorite types!

Here's the tradeoff I've noticed between INFJs and ISFJs: having more perspective almost by definition requires a level of detachment. I'm able to help people because I have multiple lenses that I can see different situations. But, being that detached, it's harder for me to be in touch with the actual sensation of feeling. Honestly, inside, I can feel kind of cold. However, I put on a act of being warm because I know that can help people.

On the other hand, my ex was an ISFJ and he was one of the warmest people I know. And it wasn't just a part of him -- it was who he was. Probably because of this, he was confused by how I could switch between warmth and detached logical precision. I tried to explain my personality to him, but it's like I was speaking a different language (Ni vs. Si). I think you can guess why we didn't work out. ;_;

I think I'm even more detached than other INFJs because of my strong Ti tendencies. But I think (I hope!) that this tradeoff means I can help people in a unique way because I can rely on all the empirical research that I've stored in my head. I can talk about your feelings and I can also back it up with evidence.

Maybe in a similar way, you're an INFJ with a strong Si that helps you ground your insights with practical experience? If so, that's a great advantage and I hope you make good use of it!