After performing my research I've settled down on Nikon 610D + 24-120mm f/4 lens + Godox V1.

My main interest of photography is mainly Landscape and Astro with a little bit of Portrait. Do you guys think, with this combination I can perform better than what I'm currently doing?

The 17-70mm you have is 27.2-112mm full frame equivalent.

The f/2.8 you have is f/4.48 full frame equivalent, both in terms of background blur and in terms of light collecting ability. Going to f/4 full frame lens is one-third stop faster. Not by much.

Let's check on a use case basis:

• Landscape: you have slightly better zoom range so picking the right composition will be slightly easier as for landscape shots zooming with your feet is very, very slow indeed. Landscape photography is not typically light limited (unless taking landscape pictures in windy low light conditions)
• Portrait: the 120mm vs 112mm you currently have won't buy you much more versatility. The f/4 you are going to get over the f/4.48-equivalent won't buy you much more background blur or low-light capability
• Astro: the 24mm will be slightly better than 27.2mm if taking wide-angle milky way photographs, but not by much and an f/4 ain't no astro lens.

I would say the kit you're planning to purchase won't be a major benefit. Of course, for full frame it's easier to buy good lenses. If you add a good portrait lens (a fast aperture short tele) and a good astro lens (a fast aperture wide-angle) then you may see benefits from moving to full frame.

But, if you plan to buy just the camera and lens you said you're going to purchase and stop there, it won't be worth the money.

Me? I would buy a 50mm "nifty fifty" and some lighting gear for your current Canon. Much cheaper that way. Unfortunately, good astro lenses for crop Canons are hard to find but the 17-70mm at 17mm and f/2.8 will be a reasonable choice.