Looks like your gym routine coincides with my morning routine, Captain…
Just to be clear, the list I provided ^^ is not a comprehensive list. I usually use dumbbells to supplement my workout rather than as the basis for it. They are good exercises, but might not be as comprehensive as you want. You’d be well advised to check out some workout plans that are based on dumbbells and/or other exercises you can do at home. Yes, you can innovate with a lot of exercises using furniture. A great example is ‘dips’, which can be done using a dining chair or low bench and provides a good workout for your triceps, shoulders, chest and upper/middle back (in that order).
Preacher curls do require something (typically an add-on to a bench) to lean over in order to provide support for your arms. It is another good exercise, though you can replace it with different types of curls until you have the necessary equipment.
I am no fitness instructor, though I’m thinking you might want to look at some kind of routine where you throw in a jog before/after your dumbbells. Since you’re not trying to lift (really) heavy weight, the cardio and resistance combined will work very well for you and get you more into the zone.
And a quick note on size… Your form is more important than the weight you lift. Make sure you can complete the full motion as intended with whatever weight you are using. Conventional wisdom suggests that you want to aim for 3-4 sets of each exercise with 8-12 reps in your set. Doing more reps with lighter weight places more of a focus on muscle tone, whereas doing less reps with heavier weight is better for gains. Given what you’ve said, you might do well to aim for something like 12-15 reps.