Why it is so difficult to rip...?

We hate your saw. Your technique probably could use some polish too (who couldn't?). But basically you need to sharpen the saw or get another saw right away.

And a sawhorse of comfortable height. Even plastic is better than nothing. Feel free to lop the legs off if they don't fit you. (Lift your rt knee a couple/three inches to a comfortable height and that's the top of your saw horse. And if you're left handed you're used to turning everything around anyway and don't need it from me.)

Pardon my prying, and feel free to slap me around, but what's your size? Are you 6'6"?  A saw that fits your frame is about a world away from one that doesn't. The standard 26" handsaw was built for your average 6' guy doing construction, give or take. Even still (I'm average guy sized), I use a 20 or 22" saw more often than a full 26". Especially inside the shop.

The big full size will flat eat some wood when they're sharp but they're less delicate (you can imagine) and less wieldy. Especially in tight quarters. A razor sharp 22 has no trouble going through anything you put in front of it and it's a real comfortable swing for me.

Another question, do you have a ballroom to work in, or a closet?

Anyway, I'd suggest you try a med sized saw that is a good old saw and get it sharpened expertly right away to get you started. Disston #7's and 8's are still a great deal. You missed getting many of the others cheap. It'll cost you more to get it sharpened than the saw will cost you, most likely, but to quote Cronkite "And that's the way it is".

PS.

Of course, if you have budget, see Mike and get you a splendid new saw. But then you take on the responsibility of caring for a great saw and be heartbroken when you mess up and plow into a nail! Tough on an old fart much less a rookie.