I didnâ€™t see a question in here, but I am assuming you are asking if anything can be done. It is doubtful that any real change is going to take place without some significant therapy. More often than not someone systematically lying, manipulating, unable to hold a job, and unable to have any intimate relationships needs a residential placement to get the structure needed to make necessary changes.
At 17 years old the clock is ticking and it is time for you and your partner to talk about what comes next. Him staying at home isnâ€™t likely to go well, and a plan is needed to have him get the help he needs. Although it is not clear from your explanation I would want to know if the biological father involved. Perhaps he needs to be if it is legally possible, relevant, and psychologically sound. Almost always this is a question a therapist would ask in such a situation.
Unfortunately, more often than not, things tend to get worse during the transition time at the end of high school. If there is any way possible you may want to check out a partial hospitalization program in your area to see what services they recommend. You may also want to talk to the guidance counselor at his high school. Even though he in school online they may be able to help with referrals and brainstorm with you about a plan for him.
Wishing you patience and peace,
Proof Positive Blog @ PsychCentral