Two problems you have:

1. You don't account for stacks sizes that well. Generally speaking, the shorter your opposition, the lighter you must stack off to him postflop.

2. You respect floating way too much. Floating is the term used for calling a bet (usually cbet) in position with the partial purpose of bluffing the next street after villian checks. You will see this a ton at 25nl.

Also, donk betting is weird. Sometimes it means big strength, sometimes it means semi-strength, and sometimes it means weakness. Typically, the shorter the stack or the more weird the situation, the less likely donking is strength.

You say you play laggy right? Stop this. Tighten the fuck up, and learn how to pwn as a tag. Somebody who plays good lag doesn't present the problems you did. Opening up your game is great, but if you do it without understanding why you'll not progress well.