Fascinating question, friend: My first question to you would be: "Safe for what?"
Semen varies considerably in color, consistency, amount, smell, etc., I would assume by your use of the word "rubbery" that you semen is thick and viscous (that mean's sort of like oil- in that it sticks together rather than being watery or runny). As long as you don't have a sexually transmitted disease, your semen should be safe for sex and whatever else you might be considering. Again, the only real criteria for safety of semen with regard to sexual activity is the presence of disease causing agents, including sexually transmitted diseases and other illnesses. Also, viscous semen may indicate that you tend to be somewhat dehydrated, that is to say, you may not be drinking enough water. You can't change most of the aspects of your body associated with sexuality. However, you can influence the consistency of your semen. If you drink a healthy amount of water, then you can produce somewhat more semen and it may be somewhat viscous. Also, the viscosity of your semen can be influenced by your diet and the frequency with which you ejaculate; i.e. the more frequently you ejaculate, the less viscous your semen tends to be.
Lastly, in a very real sense, and this is important, semen is never "safe." It can cause pregnancy and a lifetime of heartache and regret, as well as being the source of life for children. So, in that sense, semen is like anything else that carries with awesome power, it can be used for life-giving good or profound evil. So I guess the best answer is that while rubbery semen may be normal, semen is never really "safe."
As with all things health related, if the consistency of your semen remains an area of concern for you, talk to your health care provider. And remember, semen is never really "safe" no matter what its consistency, so be careful out there.
If you swallow your own semen, then no, you can't get anything new. It's quite safe. It's fairly safe, too, to swallow someone else's semen.
It is not safe.
As long as he has no STD's, it is quite safe to consume semen.
Yes it is safe as long as your partner is STD free.
The rifampin in the semen will not cause any problems, but their semen may not be safe to ingest. Rifampin is an antibiotic given for many reasons, including STD's. If the rifampin is being given for an STD then it would not be safe to ingest the semen, not because it has the rifampin in it, but because it may still have infectious particles in it.
no
Yes. It is safe if they are all free of STDs.
Yes it is safe. I do not advise doing that though. It is safe and you can do so if you wish. You cannot give yourself any infection from taking your own semen. Many males masturbate and swallow their own semen. Recent studies have found that consuming human semen reduces depression. You can find an article about that in the related links below.
Yes
Yes. The amounts that might possibly be found in his semen are at such trace concentrations it won't do a thing.
Milk is opposite to rubbery
I think it is :)