You really should not put apps onto an SD card.
They take a performance hit, whether you notice it or not.
Also, as you have seen for yourself, the space you can save is minimal at best.
Pretty much, you are trying to put 10lbs of potatoes into a 5lbs bag.
The best thing,for any device is to keep the user memory at around 70%.
That is because apps grow as they are used, and when theyare updated.
Some space must be left available for this, and remember that the system apps are always running too, so they will also need some more space sometimes.
This fact became extremely clear to me when I got a new device and had not filled it with myfavorite apps yet.
The apps that I had put on it, that were the same apps as my other devices, would get much bigger on the new device, and faster.
Well, because there is more space for them to use- and so they do.
An app on a device that is already overfull will be compromised and not able to grow as is intended.
Yes, this situation sucks.
Memory is a premium.
Yes, I have been in your position, what with the low cost devices that I use, that have limited resources.
The simple solutions?
A device with the memory required to handle all the apps that I want, ie. $$$- or multiple devices.
For $40-$50 I can get another device, and have great performance for my apps.
A bit of a pain?
But nothing compared to trying to move apps around with poor results and then constantly monitiring (or trying to) how much memory each app is using.
I have resisted the urge to get a tablet, as they cost much more than a phone that has better specs.
Use your SD card for personal media- pics, videos, documennts, etc.
Use the internal memory for apps.
If there is not enough room, then you need less apps or more memory.