No offense intended but, I don't feel you have established your priorities to the extent you are ready to make a purchase.
One of the most commonly advertised advantages to a DSLR is the versatility of the system. Not really deniable but maybe debatable IMO.
A DSLR is versatile when you have accumulated a good number of lenses and filters and flashes and other accessories. The disadvantage to all of this is you are constantly lugging around bags and bags of gear and always making decisions regarding which lens, which filter, which this or that will best suit a shot. And, in the end, quite often, you're still in a make do situation with your DSLR and the gear you don't yet own. Or can't get to in time to take the shot.
A superzoom bridge camera has the advantage of being designed by one designer or one team. All that's needed to be known about the lens was available to the camera designer and vice versa. Since a good deal of the quality of a modern lens on a modern camera is made possible by digital correction networks in the camera, this is really an almost ideal situation for a fixed lens system. Given the basic limitations of aperture which will be your most significant limitation with lower cost lenses, there really aren't that may times when a good bridge camera is out of place IMO. But, here I would say, look at the aperture limitations of most of the lenses you could afford to own for a DSLR. They aren't that different when cost is considered.
A bridge camera can be smaller and lighter and far easier to handhold at far greater magnification levels than can a DSLR with an equivalent zoom lens. Add to that the fact you will pay more for the single zoom lens (and probably still not have the reach of the superzoom) than you have for your bridge camera and the advantage to the bridge seems to me to be creeping up on the DSLR's back side.
Take for example your shot of the two individuals which you feel could have been "better". First, I would say, you have to determine what "better" means to you. In other words, what is the purpose of photography? If you feel it is all about the technical merits of a shot, then, IMO, you're missing a large chunk of what good photography is all about. It is the photographer who is important and how they envision a photo. While that get's said and poo-poo'd quite a bit, it's largely in how you have set up a scene that provides the results we want to see when it comes to technical merits.
I'm going to take a wild guess at what you probably feel could have improved that shot and say you feel some background blur would have made the subject's "pop". Well, while most superzooms do not have the fastest lens with the lowest f-stop value, you can achieve very acceptable results with your superzoom when you understand how your camera operates. For example, here are a few shots taken with a well known superzoom which demonstrate how to make subjects pop when you have the limitation of higher f-stop values;
tonybritton
If I'm guessing wrong about your opinion of the shot, then next I'd go to lighting. And, to that I'd say, most good bridge cameras have the same opportunities for lighting as will any decent DSLR in your price range.
To be clear, I'm not saying you shouldn't buy a new camera. What I'm partially saying is you have yet to fully exploit the potential of your existing camera. The time for any photographer to upgrade their equipment is when it is only the equipment which is holding back their growth as a photographer.
Otherwise, IMO, you get caught up the constant upgrade-itis of consumer grade photographic gear. "If only I had this, that shot would have been so much better." Yet, if only you had taken the time to consider a shot, probably what you already own would have managed to get the better shot.
The "coulda been a contender" shot would have likely been hampered by your lens selection in the first place if you were working with a DSLR. If you aren't using a lens set for that type of shot, you'll miss the moment while you hunt through a bag of gear to find and afix the lens you need. Disadvantage DSLR.
The other part of what I'm saying is there is not a perfect camera and lens system. You must first realize there will always be objective and subjective trade offs with any product you purchase. You then sit down and make out a list of priorities; what you you feel you absolutely need, what would you like to have and what can you do without. Then you begin to cull through the potential purchases to eliminate what doesn't fit those priorities.
If, for example, you see the benefit of the zoom power on the bridge camera, then you determine whether spending for a DSLR with an equivalent zoom lens will be of value. Why duplicate what you already own? Just as one lens cannot do everything, neither can one camera - unless you are carrying multiple bags of gear and have purchased half of any decently stocked camera shop.
Therefore, yes, buy a DSLR. But keep your bridge camera for those times when it is best suited to your needs. Don't bother duplicating gear when what you own can achieve the results you desire with a bit more knowledge and effort on your part.
If you feel you want a faster lens for those portraits type moments, buy a baseline Nikon or Canon and a 50mm f 1.8 lens. Both companies make such a set up and it's not very expensive. Realize that buying the 50mm f 1.4 lens will cost you three to four times as much and not really make for a more versatile lens in most situations. Apply the rules of diminishing returns unless you have sufficient resources to not be concerned about what you get for what you spend.
If you really need a weatherproof/waterproof camera, place that in a search engine to locate available models. Don't discount looking at last year's cameras, which can save you a fair mount of money. And don't forget to look at refurbished cameras. Most major manufacturers have them available from their own on line stores;
Canon Refurbished EOS Digital SLR Cameras | Canon Online Store
Build your kit as your actual needs develop, not just to have something. Right now, you have a fairly long way to go with your present equipment IMO. The number of occasions where a DSLR would have taken a subjectively better photo is minimal IMO when I look at your provided examples. It really is the photographer and not the photographic gear which makes the shot.