You are looking for a very simple answer to a very complex issue. There are 3 factors in remaining healthy. One is lifestyle, such as weight and smoking, another is age, and the third is plain luck (including genetics.) A person can be young and 600 pounds and be quite healthy. Another person can be thin (or fat) and suffer a slew of age related problems, especially orthopedic mobility issues. Or a person can develop issues over the years that can be complicated by weight. So gaining now may have no consequences, but if you get older or hit bad luck there is no guarantee you will remain healthy.

No. What someone is, and what they prefer are two different things. Some large people don't like to call attention to their weight by dating another large person. Some large people grew up learning not to like themselves or other large people. Some feedees want all of the food and attention.

Does anyone know if this will give you manboobs?

See a doctor.

There is no guarantee that anyone can get up to a higher weight, and even less of a chance that someone can get back to their old weight. Yoyo dieting is unhealthy, and people who continue to do it, end up getting less muscles and more fat as they do it.

You lose fat and muscle, but gain only fat.

That is true in all kinds of websites. People confuse fantasy with reality.

Yes.

My exwife took a bath and pulled the plug. Only the water from the front half of the tub drained out.

You and your boss got high at work, and then he wanted to make you pregnant? Sounds like he can get into a lot of trouble for that.