It all depends on how far do you want to go with your energies and time for your dad. If you love him to fully commit this is my opinion on it: Analyze everything, his natal chart, tendencies and the conjunction of events that were in the past and are in the present. Take notes and observe how it is manifested in his mind and reality.
My first suggestion is to clean him with extreme intent of mental and emotional blocks that govern his situation right now. That implies a lot, it implies even more burst of emotions and dystopian visions that may come to surface. Along with cleaning and destroying chains of its past and people you need to create a protective energy pool only for him. A lot of fire and air as attributes. (Sowilo, Algiz, Raum etc.etc. combine them in your working and also start in favorable signs of the planets and also in his future planets to be)
After safe checking these things or congruent to them, I strongly suggest Wunjo rune as a long term working on him, with affirmations that will heal his depression and tendency to have it. Also this will cause bonds to happen, friendships and healthy relations. This will help a lot. You also need to act physically besides spiritual, by being close to him and create pathways and inspiration for those energies to kick in.
Also you can use some fire runes as more workings to spark his desires and make him be active, expansive to his desires and goals. From time to time it will make an utmost difference if you'd gift him some of his desires by magical workings to manifest them.
Work related- this is easy to obtain by programing any raw energy to get him a pleasurable and good workplace and job. You can use Fehu and Sowilo with Aum. But always renew that pool of protective energy. Your goal is to minimize bad fated tendencies and work around them.
Witch related - I suggest you go and blow some energy hits if you find that she caused it or had any part in it. You can raise and store energy and ask a Demon to help you direct and revenge this situation. Please be proportioned in this aspect, maintain a high moral ground.
You should be aware that everything you do by your power will make him without much discernment or control. You will notice restlessness and other symptoms of your working on him. Not everybody can handle big exterior forces even unconsciously. You absolutely need to know what you do and be at least in the knowing with everything I stated. You need to be in a high position to assume this responsibility!! If you don't have the means spiritually, don't worry - it means real motivation for you to use that will benefit you and your family in the end. Study and practice, then take challenges by its horns. The runes I suggested may not be good or useful in this case as solely an opinion, this should be only your decision. You can't control everything, you should also leave a sense of freedom in his "fate" of him, more of a "kick started" is what you need to produce.
Also don't be afraid to get help from Satan and Demons. If you don't have time for any long and committed workings, just use Wunjo on him.
I totally hope you'll fix this and I hope you and him find happiness and joy in life.