Before I understood how alcohol takes control of the person I too was upset when my aw would get "dolled up" at home before leaving for her rendezvous with her drinking women and MEN. Then to add insult to injury she'd ask me for the car keys.
The bottom line is alcohol is in control and addiction and promiscuity go hand in hand as any addiction counselor can tell you. If you confront him he will simply do what addicts do, LIE, twist,get resentful and angry, etc etc. The boundaries thing is best as is letting him feel the full impact of the consequences of drinking.
Unless my aw decides to sober up and recover I am perfectly at peace with myself living apart because living with her was HELL. I cannot live with the person alcohol is steering. What alcohol did to her believe me let some other guy deal with. Most likely she has an alcoholic/addict boyfriend but "they can keep each other" I do not and will not live that way anymore.
If you cannot detach enough and/or accept what alcohol does to a person you may wish to start documenting his conduct for potential use in court.