Monique Dress - Muslin #1

Bon matin! Talk about an ice breaker post ; I started my Serendipity Studio Monique dress and I am experiencing some trouble to make it fit! So here is my attempt at documenting my alterations and progress, I hope some good seamstress might stumble onto it and give me some advices! 

Pattern Size Choice
At this time, my measurements are : 41-33-40, with high bust of 37. So 4in difference between high bust and bust means am a D cup... (my bra is 34G) Looking at the Serendipity Studio Monique Dress pattern info, I decided on the size LARGE (40-32-42), with 1 in FBA. I knew I would have to fiddle with the waist a little but since its a straight band... 

Full Bust Adjustment (FBA)
It is my first FBA. I'am not sure if I should have tried a X-Large without alteration first. But since the pattern is designed for B cups, I knew it would need tweaking anyway...

Here is what I did to the front bodice pattern piece :
1- I sliced from the Real Bust Apex (RBA) to bottom seam and from RBA to armhole at about a 30o angle. Then, I spread 1 in from bottom to RBA and tapered to nothing at the armhole.

2- To realign the bottom seam of the bodice, I sliced from RBA to the Center Front (CF) fold & spread 1/2 in. Redrew the new dart at 1 1/2 in horizontal distance from RBA, with width of 1 1/8 in each side.

FBA and length alterations

3- To match the side seam between the bodice front and back pieces, I added 1 1/2 in to the back bodice armhole and removed 1 1/2 in to the front bodice armhole (as seen in Fast Fit, by Sandra Betzina). I drew the curve by both eyeballing it and using the original patterns pieces since I do not own a curved ruler yet...

added half the difference to the back and removed it from the front

Now the side seam match

Bodice Muslin #1
I made a muslin of the bodice and it kind of worked out OK. The fabric is medium cotton (I think) at 2$/m from a Fabric remnant shop in Montréal - I bought about 10 meters to make some muslin for a few projects and I plan of wearing my finals muslin afterward, I LOVE the color!

My problems with the first muslin :

• there is a gap at the armhole;
• the under bust seams is not quite under;
• the waistband is about 3in higher than my natural waist.

The waist band is just pinned, white elastic is at natural waist

I just pinned the back too, no zipper yet

Armhole Gap
This is my major problem! I tried to pin it, but the resulting dart intersected the horizontal bust dart - I can't do that, can I!?! What should I do about the gap in the armhole? Is it because I totally ignored the original dart when doing my FBA? Or of poor retracing of the curve of the armhole? Or it's the chosen FBA method that inevitably add more fabric around the armhole? Or I started with a size too big?

Under Bust Seam Too High
To get the under bust seam lower, I plan to slice horizontally between the horizontal bust dart and the vertical under bust dart and to add about 2 in of length.

Waistband height
Because I'm not sure a slightly gathered A-line skirt starting a mere 3 in under my bust would be flattering on me, I am also thinking to lengthen the waistband so the bottom of the waistband hits my natural waist. But I will reassess the waistband height AFTER resolving both previous issues...

Any advices? Merci!