Yes, if OW is a drain on him (financially and emotionally demanding) then hopefully he doesn't have the stamina to stick it out, long...
but...
how long has he said he's not been happy with you? If he were a sane man... then you could expect that he has the stamina to stick it out (almost) as long with OW...
alternately...
if it doesn't work with OW... and he sees the colateral damage... and really looks at and says, "oh wow...! I can't overcome that..." he may just find another OW or decide to stay away...
unless the collateral damage goes away...
That's not to say you hold him harmless and it's not to say that he shouldn't have to work for it...
but... you need to be an attractive option... one that is more attractive than the challenges that might face him if he DOES choose to come back...
and if he's NOT sane... if he is MLC... then understand that once he's ready to come back into the R... when he is ready... done with the MLC... he is likely not going to be the same man that you married... this is not uncommon... the alien doesn't necessarily leave... it just becomes less volatile...
You may have to wrap your head around the possibility that your H is really "gone"... that his physical body will never contain the man your married. That a R with him will be no different than building a new R with someone else... So any baggage or collateral damage... well... it won't really be his...
Time to do a little house keeping while he's on vacation...
GAL can be hard, but it doesn't have to be. You'll eventually find your groove. Don't beat yourself up because your priorities are getting used to being single and being a single parent. Things will get better... and then will get easier... and eventually, you'll be a better version of the past you...