For specific questions about the completion of the I129F form it is highly advisable to consult with an attorney in private for a thorough review...

I am an american citizen, its been 14 years i have left the US, now i am an adult is there any problem if i come back to US now?

As a USC you should be able to enter the US freely despite the length of time you have remained outside of the country.

When I fill i130 form which uscis should I mail? I live in Maryland

Refer to the USCIS instructions under "where to file" which will indicate the appropriate address.

Will i get my citizenship after my interview ?

You should discuss your case with your hired attorney as s/he knows what to expect best.

USCIS should be sending the I130 approval to the NVC for further processing and you should not need to file Form I824.

Without the underlying I130 the I485 will likely be denied anyways. You can write to USCIS with a request to withdraw this application.

Citizenship through marriage or asylum?

No you can pursue your citizenship based on marriage to a USC but the timing of your 5 years eligibility may come sooner if you haven't already...

Anyone deal with Canadian Immigration or Permanent Residence Status with Work Permit?

You should consult with a Canadian immigration attorney as this forum deals with US law.

You appear adjustment eligible despite the visa overstay as you presumably married a USC in good faith and entered the country legally. It is...

How do I get my job to give me income verification letter for immigration?

You can provide your employer with a written request for the job verification letter. An attorney can assist you in drafting this letter.