I will try my best to answer this questions but first I must say that-honestly, if you are thinking this in depth then you are not enjoying the realtionship as much as you can but rather worrying. Please don't take offence to that, as it was just my opionion and may not nessasarily be true.
1. How do you gauge the seriousness of a relationship?
A: What reason are you in the realtionship for? Are you looking for a friend or a partner? If you get jealous that he is talking to another gal, I'm not sure that is really a 'real, healthy relationship' but rather someone that you feel you need. For, me- sometimes when someone talks to another person *whether it be a serious relationship or not* I tend to get jealous because I feel I want the attention of the person on me because I almost need 'confort' to know I am 'visible'-so to speak.
2. What is love?
I think it is an emotional attatchment; a feeling of being one.
3. How do you know when a relationship crosses into love?
Again, I ask what are you in the relationship for?
4. How do you differentiate between love, lust, infatuation, adoration, and any other state of a relationship?
For me, infatuation means: "Oh-my god, he is soo hot I would love to have him for a night".
As for the meaning in Dictionary.com it means: "An object of extravagant, short-lived passion."
Lust-*according to dictionary.com* is: To have an intense or obsessive desire, especially one that is sexual. I personally would say that it is a 'lust realtionship' if what you are looking for is one specific thing, most likely sex.
The difference between adoration and love is hard to differentiate but I would say that love is stonger than adoration.
5. Let's say that two people had been dating for 5 months, and one of them was going to have a birthday... What level of gift would be appropriate?
Depending on your age has a lot to do with this answer. I think a thoughful present is much better than an expensive one. Perhaps, instead of buying him an outfit from Abercrombie and Fitch you can take him to dinner and a movie. This way, you can spend time together AND most likely spend less money. For me, I would prefer to have a good time with the one I love/like that I will remember the good time than clothes that 'someone gave me for my birthday.'
Sorry for the long post and I hope it helped but then again- what do I know? lol
Have a good day and good luck!
"How bout a little black dress?"~hannahshule
"I have a penis, not a vagina." ~munkustrap178