Most all gun take a little extra effort to seat the mag fully, with a full mag and the slide closed. Open the slide and the mag will seat effortlessly. If you think your shield takes effort (and I know what you mean, mine is the same way), you should try a Glock 30 in 45 ACP. It starts to get hard to insert about a half inch before fully inserting.

As for the mags, load them, and leave them loaded. When you're done shooting, reload the mags and let them sit.

As to the slide release, Are you referring to releasing the slide? Or are you referring to locking the slide back? I can't see any way there would be tension to the slide lock when trying to lock open. But if you are trying to thumb the slide closed with the slide lock and it's hard, don't do it, just sling shot the slide from the back. I have several pistols that I cannot use the slide lock to release the slide.

__________________
Rod
M&P 22A, 40c, 15A, 15-22