I thought I've been looking for a good password manager, but I'm not sure that's what I really need.

Here's my use case:

• I currently have a Google Sheet in my Google Drive that contains all my ID/passwords for everything
• In addition I have personal info in there like SSNs and Credit Cards #s
• I want to be able to have instant access to all of the info from my ancient iPhone and my laptop

Things I've tried:

• I messed around with Last Pass a bit and found it couldn't actually fill in the passwords in the apps I was using so I'd have to manually type them, which is a deal breaker for me.
• I've been using FireFox's LockBox and it's a bit better on that front but doesn't actually remember what the password goes to the app so I have to look it up each time, but it does populate them in the appropriate fields.
• Password-protecting a Google Sheet is apparently impossible but was a solution I was after for some time (Excel and Libre can do this..so +1 for software)

Other info:

• I am currently using an iPhone 5 but I plan to "upgrade" to a Samsung Galaxy S7 sometime in the near future. Perhaps that's why the functionality of these password managers seem so inconvenient for me? Would they work better on a modern phone?

What I'm after is perhaps two solutions:

• A password manager that crosses the bridge from desktop FireFox to the apps on my phone, and fills in the password for me automatically. That would allow me to feel like I could move to more random passwords for things.

• Some encrypted, password-protected site/app that could store plain text notes for sensitive things like SSNs and Credit Card #s that would stay in sync between a laptop and a smartphone.

Go ahead and mock me for my terrible security and ancient phone. I deserve it! But when you're done, I'd appreciate some guidance.

EDIT: Sounds like first priority should be to update my phone. Then there appear to be plenty of options to try. Thanks everyone so much!

I'm gonna have to buy a new smartphone soon, but I want to be able to keep that as long as possible. From my viewpoint, there are mainly three aspects to that: performance, software and battery lifespan/replaceability.
Do you have any recommendations (what I was originally hoping for - but didn't find - is a mid to high range phone with a maintained lineageos build and a replaceable battery)? And what are your ways to handle the problem of the user experience on smartphones degrading so quickly?