Some thoughts:

Your second option R10 would be much better. R10 works together with your upper side and your lower side, building a large framework on the right. White would have to come in to prevent this, but with R10 in place whites invasion group could be easily attacked, allowing you to make profit.
R14 on the other hand, the move you played is only working together with your upper side, leaving white enough spaces to invade the right side and destroy your potential without much risk.

I don't like this move. After whites invasion you have two options, defend the corner and let white escape towards the middle or let white take the corner and take the influence - you decided to take the second. But because of whites previous invasion on the right side, you don't have a large framework, with which the influence could work together. P8 is really close to your new influence, which means you don't get that much points from it, probably less than white gets from taking the corner. So taking the corner would have been bigger.
Also when taking the corner, white would have to extend towards the left side to make a base, but there you already have L3. And if white would try to escape upwards towards the center P8 might become useful. All in all, if you would have defended the corner (R3 or R2, not sure about the correct tactical move) you not only would have gotten secure profit, but also made white weak.

Yes i would also say this is a mistake. C14 and C6 are both on the third line which means both corner are closed by white. Then there is nothing to be gained by playing near them, you don't threaten whites corner, so white can easily play the pincer to attack you.
If you want to play on the left side, to prevent white from taking it, i would have played D10. For one this is the move i would also like to play as white on this side, so by playing it as black i can easily prevent white from doing so. Another reason is, that because if invaded on the third line white would definitely pincer and there is not enough room to make a base. So every invasion black could play there would be attacked, allowing white to profit from it. But D10 is on the fourth line, which makes it more like a reduction than an invasion. D10 doesn't have to make a base, it can easily escape towards the center to prevent being attacked.
Another option, instead of reducing whites left side, would be to increase the lower side moyo you built with P8 and P3. A move around H4 looks good. It would also defend a possible invasion point of white (around H3).

Yes J5 is to far away from the white stone to really threaten it and it leaves the possible gap at K4 (Elephant jump) which white could exploit later or force you to come back (losing sente). The keima looks much better.

The move you actually played is big, but i would agree that extending once more is urgent. You know the proverb "hane at the head of two stones"? Well your two stones are already haned at the head (J4) which means allowing white to play J7 would be really painfull.
White would not answer with H7, that is pushing from behind. Instead white may play a knight move (G8), jump (H8) or play tenuki, but still extending for black would be good.

Connecting is better. If you push white will play L18 and easily life on the side. Then you would again trade territory for influence. But with P12 and the possible hane at J7 i feel that white can easily erase your influence, so taking the secure cash is better. Also thanks to F15 the whites group now has a harder time to escape, which is good for you.

That looks really slow and small. I can see that you try to "cash in" your influence, but with the stable whites group on the right it is just not possible (Thats why going for influence at the top was not a good idea). If you want to use your influence at the top, then attack whites group on the right, starting with the peep at Q11. If white blocks at R11 to secure the base you can cut through and get a really nice moyo in the middle. If white answers the peep with Q12 you could try to rob whites base with S11 or S10. It is probably not possible to kill this group, but attacking it will allow you to secure your lower right moyo while white will (thanks to your upper side influence) play moves that make no points at all. That is what attacking is all about.

Yes, extending. Hane at the head of two is already painful. The second hane (hane at the "ass") is even more painful.

was already a mistake, you won't make it better by trying to save it. Just play K8 and protect your moyo.
That's it for the per-move comments. I may not be the best to give advice about the opening (that i'm pretty weak at it) but it seems to me you focus to much on influence, but then can't really use it well. Influence is used for attacking. The basic idea is to build a large framework with it, so big that your opponent has to invade - and then you use your influence to attack its group and make territory elsewhere.
If making such a big framework isn't possible anymore, because there are living groups of your opponent in the area, then don't go for the influence - take the territory instead.
Don't forget that if you are building influence you are paying for it with territory you give to your opponents. For this trade to be good you have to make a lot of points with your influence.