Ok, so let's drop the assumptions and see what we are left with that can't be disputed;
There is experience of this human being.
There is experiencing (now) and experience (memory)
The "of this human being" is disputable. For a start experiencing requires both experiencer and experienced, so you tell me where does one stop and the other start ?
Are they actually divisible ?
There are all of these things around it that exist, ...
It does seem such an obvious statement, doesn't it. "Things exist...", but this too is a presumption. You presume it exists because of thoughts that arise as a result of sensory input. Take a mirage, for example. You see something that your brain interprets as water. There is no doubt that what you are seeing is water out there. If you are thirsty then your body will (as a result of thought) crave drinking more intensely, thus reinforcing the accuracy of what you (think you) are seeing.
Now a mirage might be an extreme example, but i put it to you that there is some of that in every seeing that occurs. Take a tree, for example. You see a tree. The label 'tree' gets applied, then there is an opinion about that tree, say "it has nice form, or pretty colored leaves etc", but from the moment the label was applied the existence of the tree was (almost) entirely in the head.
So yes, things exist, but not in the way we imagine them to.
... and the human being is the central point of the experience.
Do they exist (for us) when we are not interacting with them ?
Take the old Zen koan "does the tree falling in the forest make a sound if there is no-one there to hear it?"
Air vibrating at a certain frequency requires an ear to transmit those vibrations to a deciphering apparatus and it is that apparatus that actually generates the sound. The brain then uses experience and logic to give meaning to it. Just as with seeing the tree, a sense input (eyes) and deciphering apparatus are required to 'make sense' of light vibrating at a certain frequency.
So let's replace "human being" with organism, and let's replace "central point of the experience" with an indivisible (with the so called object) involvement of experiencing (a verb)
There are senses in the human being that experience everything and thoughts that talk about things experienced.
Yes, thoughts arise About, what is now a memory. This is a new and different experiencing.
Check these things for yourself. Don't just think about what i say, and certainly don't believe anything.
Does true look a little less certain now ?