3 Yes it is possible to transmit the virus before seroconversion, but you don't need to worry about that as your sex was protected
3- no ( if protected)
4- negligible risk
Thanks for answering! I have another question, since we all know that any oil-based products such as lotions weakens the condoms, Is it possible for a condoms to have small holes if lotions are used as lube?
When there is broken skin anywhere on the body, this is an entry for viruses and bacteria to enter. Always keep broken skin clean, dry and covered to reduce the risk of getting infected. Check out cat scratch fever, cellulitis - these are not sexually transmitted diseases, but these are infections that are caused through wounds in the skin.
Not matter what type of bacteria or virus a person has, a person without any symptoms can still be a carrier and depending on your immune system you at a high risk of contracting whatever that bacteria/virus is when you come into close contact - by skin contact, exchange of fluids (through kissing for example) and sometimes by using the same towel, sharing drinks out of the same utensil. When someone coughs or sneezes the virus/bacteria is expelled into the air that you breathe and in turn you are then exposed to that bacteria or virus.
Even with protection, there is always the risk of getting some skin contact. The risk is small but any open sores or wounds that you could be exposed to would be a high risk of you getting contaminated.
In your other post you mention about having symptoms with urination and in your penis. What that being the case, stop trying to analyse things and make a very URGENT appointment to see your doctor and the GUM clinic to get checked out. If you have got any bacterial infection, it is important to get the appropriate treatment as soon as possible.
With regard to your open wound on your thumb - if you notice that the wound is not healing, is red and spreading, the wound is painful and or throbbing or if any discharge starts to come from the wound, seek medical attention immediately. This would indicate the wound is infected. Infections can spread and can become life threatening - yes even from a very tiny scratch (this would not be related to a sexually transmitted disease, but nonetheless I feel you need to be aware that small scratches or cuts to the skin can sometimes become very serious.