Welcome to the forum!
Regarding the login page, it is indeed secure. In the screenshot I just made, you can see that the address is https. I don't know what link you clicked to get here, which still uses http. But you can just add the "s" manually (and then press Enter), and get to a secure page. Or you can log in from the dark blue box in the top-right corner of any page. (Except for embedded images, or other things which are beyond my control, the entire site is secure. I have an SSL certificate for the whole server.)
I also have trouble when trying to add new gradient stops. I'm with you, everything I've read says double-click on the gradient handle, to add new stops. But sometimes, it just does not work. I've even posted messages on the mailing list, to ask developers. I don't know, maybe I should make a bug report. But the problem is that it's itermittent. So how could developers fix it, if they can't reliably reproduce.
But fortunately, we have a fix. On the Gradient tool control bar, there's a button for adding stops. And that's what I use. Just select a stop, and click that button, and a new stop gets added.
There is a slight problem with that button for me. I'm not sure if I reported it, but I might have. In any case, that button only adds stops towards the end of the gradient. Like if it's a default, left to right, linear gradient, you can only add stops to the right of the selected stop. The next stop that's added goes halfway between the last stop and the selected stop. And it won't add stops to the left at all. I think they should be added in a different way, but of course I have no control over changing it - just the request I think I made.