I don't even know how to respond

[sunset03]

Hello!  I am just at a loss for words and coming here to seek some support from others who possibly have gone through/going through something similar. 
My boyfriend of 4 years had been diagnosed as bipolar and OCD with borderline personality disorder issues several years ago.  He also struggles with alcoholism and drug addiction.  He was raised with absolutely no coping skills, so when he feels his world is out of control, he does not have the proper tools to cope and always chooses drugs and alcohol as his coping mechanisms. 
He is having a particularly difficult time this year as him mother passed away from cancer at the end of Feb and he cannot see his father and older handicapped brother (who live together) during this time of isolation.  Long story short, I have been searching for a new career path or at least a new interest as I have been feeling very stale in my job the last couple of years or so.  In my boyfriend's profession, he is required to get a re-certification every 2 years.  So as he was doing this, I thought perhaps I should look into getting myself certified as I have had a growing interest in this particular field over the last 4 years and it is actually part of my daily routine.  I came to him about a month ago to talk to him about this decision as he has 26+ years of experience in this field and told him my feelings to also look into joining this field, receive a certification and perhaps we could even team up together and do something together.  He told me it was a great idea, to go for it and that we was proud of me.  I have been doing the online reading and studying this past month and he had continued to tell me that he was proud of me. Yesterday was a very bad day for him as all things had come to a head and he was feeling out of control.  He began to rage and started texting me (and a couple of other family members) messages threatening to hurt himself.  He has done this about 6 or so times in the past, so I have had experience with this.  However, he proceeds to tell me that he can't believe that I went ahead and chose to go through with this certification process and that it is now "killing him" that I'm doing it.  When I reminded him that it was something we had discussed and he gave his approval and that he said he was "proud of me", he said that it was something I shouldn't have even approached him with in the first place as I should know better than that because of how "sensitive he is" to the situation.  He also said that he doesn't understand why I'm doing it (mind you, we did discuss this initially) as I don't even have a degree in the field like he does.  Now, in my initial response to him, I don't feel like I used the proper word and perhaps triggered an even more resentful attitude from him.  I used the word "lied" and said "you should have told me the truth from the beginning, instead you lied".  I do realize there was a better way I should have said that statement.  I feel very defeated and even foolish now for thinking that I should have moved forward with this endeavor.  I thought it was something I could be great at and would be something new to learn and possibly make a career out of.  Now I just feel stupid about it.  I don't even think I can cancel the online certification or get my money back.  What my question is, how do I even respond to his behavior toward this?  Do I even need to respond?  Is this a behavior of the BDP and what would be the "right" response to this?  If anyone out there has any similar experience they could share, I would be most grateful!

[RELATIONSHIP PROBLEM SOLVING]

RELATIONSHIP PROBLEM SOLVING This is a high level discussion board for solving ongoing, day-to-day relationship conflicts. Members are welcomed to express frustration but must seek constructive solutions to problems. This is not a place for relationship "stay" or "leave" discussions. Please read the specific guidelines for this group.