The body will try to adapt to just about anything, so it will work at least to a degree if you eat enough (which you are not, otherwise you’d be gaining weight past 75Kg, that’s purely an issue of your diet) etc…
Okay, 3 days like that is entirely possible, but really far from ideal… Are you sure 4 days are impossible? Why?
For your three days you could do…
-Bis, Legs (bis after deadlifts if you do them here, though I’d add them on back day perhaps as your first back exercise, that way your heavy work is spaced out a bit over the week)
or a traditional…
-chest, delts, tris (not everyone’s shoulders can take that)
You can train your abs whenever you want. But seeing them? That will require stripping bodyfat. Diet again, but you’ll have to eat differently for that than you would for getting past 75Kg’s.
A 2-way split can be done as well over those 3 days… Chest, Delts, Tris, then Legs, Back, Bis etc… But that’s a lot of work in one session on one of the days at least no matter how you split it up.
Full body is something I would not recommend, especially for serious trainees, but whatever… Some like it.
One more possible thing is doing the powerlifts (or variations) on wednesday and maybe some face pulls and such, and then doing your other work split up over the other 2 days.
But really, best thing you can do is make it 4 days. Gives you a lot more options, among them some of the best approaches out there.
As for your diet… Protein at least 1.5 g per lb of bodyweight for you, 1.8-2 if you are serious about this and are on a demanding routine etc, rest (carbs, fats) as needed to gain weight, don’t cut out fats.
For cutting bodyfat there are many options… Carb cycling (somewhat complicated) or Skip’s approach (skiploading, watch his free DVD , the seminar and addendum part) work well for example.
I like skip’s better, strength doesn’t go down so badly and it’s easier to follow than other approaches to dieting down.
And make sure you are getting stronger on everything. (at least while gaining weight)