I can clarify one other point, which is about the anesthesia. When you say "surgical anesthesia" usually that means an inductive, such as Fentanyl or more likley Propofol, then maintained by something such as Halothane. In surgery you may also be given an analgesic and paralytic such as pancurium bromide, which then requires intubation. This is all necessary for a procedure such as having dental work (of virtually any severity), or a colonoscopy.
In this case, while I cannot say exactly what your doctor will use, the general approach is to give a combination of Versed (Midazolam) and (a small amount) of Fentanyl. The effect is that of a powerful dissociative benzodiazapine which often causes minor retrograde amnesia, and the analgesic and soporific effects of fentanyl. This presents very little risk to respiration or blood pressure, but it has the effect of making the experience "a blur" and reducing or eliminating any discomfort. The effects of these drugs are also highly preferable to those which disrupt the activity of the hippocampus such as the aforementioned halothane.
In my opinion, and it is just that per forum rules, this is not thing. While I cannot offer a diagnosis over the internet (and couldn't from the information given anyway), it seems that this is an important step in determining the cause of what is clearly a clinically significant GI issue.
As for hemorrhoids, it would not shock me that they are present in someone who I'd guess, strains when going to the bathroom, or has spastic activity which causes the same. They can be corrected surgically, but there is rarely a need, and certainly a doctor won't try before the cause has been addressed. If you no longer have to strain on the toilet, you may well find they shrink and "leave" of their own accord.
For the bloating, I wouldn't worry, as one generally evacuates the gas once the sedation begins to wear off, through the process of copious farting. I would add that none of this should be embarrassing, as everyone who can afford it will or has this procedure done, usually more than once. The drink to "cleanse" is no fun at all, but I think you'll find that it is easier for you than most, as you already have these GI issues. What's worse, drinking what tastes like stale lemonade and fasting while crapping a bit, or this ongoing problem?
I will put one thing out there, which is that I assume you've had your "iron binding" levels checked in your blood work, and are not anemic? This would be ferritin levels, serum iron levels, a electrophoresis to check the structure of your leukocytes, and hemoglobin/hematocrit numbers. From what you've said there has been no finding of occult blood in your stool, but the hemorrhoids could bleed occasionally.
Finally, I don't see either procedure could have the slightest effect on your chest, sternum, ribs, intercostals or related structures. Just speak up if you feel that sedation is insufficient, experience pain, and so forth, but the procedures themselves are as safe as it gets. You have more risk of pain from having third molars extracted and being left with a "dry socket".