Reading your post reminds me of me, I was like you are - arguing from every side, and it was killing me too and what I worked out is......... I was trying too hard .........far too hard.
You see what you have developed (like I did) is an anxious obsession to NEED TO KNOW NOW how everything is working, is put together because you don't know HOW and it is confusing the hell out of you and so you think that if you sit and try to work it out then everything will be OK. Once you've worked it all out you will have this master plan to follow and all will be well - you will have worked out the meaning of life and so you can RELAX and just follow that - right?
Well what you've done is set yourself a challenge that can never be met - nobody can tell you the meaning of life and you won't be able to work it out either because it changes all the time and is different for everyone - so how can that be worked out?
You see there isn't one set meaning to life - we all have the free will to make life mean exactly what we want it to mean - and the meaning of life is flexible and open to review as well, so it can mean one thing this year and mean another thing next year once more knowledge has been gained, etc. etc.
Example I used to think life meant one thing - then I had kids and BAM life meant something else entirely and literally the meaning of life for me changed. I noticed that and realised that the meaning of life isn't a fixed, rigid viewpoint that we all must adhere to, AND that is because we have been blessed with the freedom to choose what we want it to mean to US and US alone and THAT in my opinion is the free will you are talking about.
We can think what we want, do what we want and the only rules are that our actions will have consequences. WE reap what we sow.
So you can choose life to mean whatever you want and that is true freedom. Now this doesn't mean that you can make life do whatever you want it to do, and it doesn't mean that tragedies won't happen - but it does means that you have the free will to make of that what you will.
So it you want to decide life means nothing and it is totally pointless - then you are right it will mean nothing and will be totally pointless - that is free will. But is that view point just a current perspective? and can that perspective change over time? YES, absolutely so be careful if you think you have got it all figured out, because you probably haven't - that will just be this years viewpoint and that viewpoint is very likely to change.
So Cuch is right, if you want to explore the meaning of life, nature and all it's working, etc. then try looking at it from another perspective - Buddhism is a good way to go as it is a different viewpoint than the "normal" western perspective and will challenge you to look at your current perspective differently than you do now.
But Cuch is also bang on the money that you have to be careful not to let theories drag you away from life. We need to be healthy looking at what life is about, but we also need to be healthily enjoying it as well and I think that is the point, that is the meaning of life - YOU ARE HERE - you are NOT not here, so if you are here then why not RELAX and just enjoy what here has to offer? Ok so it all seems strange, weird and complex - but what does that matter - should that really stop us enjoy this gift of life?
I will leave you with some of the Buddha's quotes to consider - but don't get anxiously caught up in trying to figure them out - it might just send you nuts
1.(after being asked about doubt and worry) "Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment”
2.“It is better to conquer yourself than to win a thousand battles. Then the victory is yours. It cannot be taken from you, not by angels or by demons, heaven or hell.”
3.(on living) “It is better to travel well than to arrive.”
4.“Peace comes from within. Do not seek it without.”
5.(on success) “The only real failure in life is not to be true to the best one knows.”
6.“The way is not in the sky. The way is in the heart.”
7.“There is nothing more dreadful than the habit of doubt. Doubt separates people. It is a poison that disintegrates friendships and breaks up pleasant relations. It is a thorn that irritates and hurts; it is a sword that kills.”
8.“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”
9.“We are what we think. All that we are arises with our thoughts. With our thoughts, we make the world.”
10.“What we think, we become.“
Hope it helps