Knowing how much you're lifting
I am reasonably new to lifting heavy things (well, new in the sense that I actually sort of know what I am doing now and follow advice instead of randomly lifting weights).
What I am having trouble with, when trying to keep track of what I'm doing so I can see what works, is actually knowing how much I am lifting.
On machines, if there is no unit of measurement, is there any way of knowing what it is, short of actually weighing the weights?
Also, when doing things such as weighted squats, lunges etc., how much does my current body mass factor into that? E.g. at 230lbs I am doing squats with about 10lb in each hand (so 20lb total).... is that the same as when I am 180lb doing squats with 20lb total? Or would that be considered a decrease in strength?
And thirdly, you cannot compare weight lifted on different kinds of inclines, correct? E.g. the weight I can do on a seated leg press is not the same as what I would do on a vertical leg press? It also has to do with how the machines are set-up as well, like the cables going around pulleys a certain amount of times etc. - meaning you cannot compare weight lifted between 2 different machines with different set-ups? (Physics always was my worst subject).
Didn't really know where else to ask these questions and when I google them I'm not getting much clarification. Any input would be great!
Also a slightly off-topic question, while my main goal is to lose fat, should I be expecting strength gains, or more like strength maintenance, or strength loss? I still have about 80lb of fat to lose.