How to maintain the knife? What am I missing, and what am I doing wrong

I've been cooking for a long time now, and I've been the proud owner of entry level chef knives for the better part of a decade now.

Last month I've ordered a new knife, a KAI Saki Magoroku Redwood, which is not their cheapest knives, but also not their Shun series. I figured, it was better than what I had, its steel is harder, and angle is steeper, and it will hold out better.

Nevertheless, I use my knife a lot (about twice over three days on average, maybe a bit more), cutting a lot of salads, meat, chopping garlic, etc. So you'd expect that the edge will lose its sharpness at some point.

And indeed, after four weeks, the knife no longer slices tomatoes. It started out great with tomatoes, then slowly it became an easy task depending on the point of ingress (so I'd run the knife gently, and it would eventually slice). But now the knife just can't break the skin. This is not only frustrating (who wants crushed tomatoes in their salad?), but it's also dangerous.

Everything else gets chopped very nicely. I don't have any problem with scallions, cucumbers, spinach, garlic, or any other thing I'd normally chop.

I tried my sharpening rod, but to no avail. It made an effect, but not enough to keep me from fearing for my fingertips. My sharpener is a pull-through "Victorinox Sharpy", and I fear that I will mess something up with the knife if I use it.

What can I do better to maintain an edge for longer?

I'm cutting on a decent wooden board, nothing frozen, no bones, washing my knife immediately after use, and storing in its KAI blade guard in the drawer (in a way that also minimizes movement, just in case).

How do I make it sharper?

The sharpening steel is a bust. Maybe it's because it's two years old, and wasn't the best quality to begin with. But maybe it's something else. I'm not sure if using the Victorinox gadget will solve this, because pull-through are normally set to a specific angle, and it might not be the right one.

The KAI manual website says to sharpen (on a whetstone) at a 15 degrees angle, but they don't specify the series of the knives. I couldn't find the angle information on any website, except one which said, oddly enough, 22 degrees. (This despite the KAI Wasabi series having 15 degrees angled edge. So I'm not sure if that site was right.)

My current line of thought is to buy a whetstone and learn how to use it with my old knife, and then sharpen the KAI. But that seems like a lot of work that I should be able to avoid.

Any advice?