I think we can stay with [sK] for such a rare form. The 進退これ谷まる entry is rare and marginal and really has no impact here.

@@ -16 +16 @@
-<ke_inf>&rK;</ke_inf>
+<ke_inf>&sK;</ke_inf>

On further thought, I'm removing [sK] from 谷まる in favor of [rK].  It is "correct', and this form *does* appear in yourei, even in recent works. You can even find the off appearance in wikipedia.

There is another recently added entry "進退これ谷まる".  If we [sK] 谷 here, it will looks very strange for it to appear there.  And if we go strictly off of statistics, there's an argument to [sK] 谷 out of the きわまる entry itself.

Note: for statistical purposes, only 窮 and 谷 are actually considered analogous by Japanese people, so their relative statistics should probably not consider the more-common 極, which throws off a lot of numbers.

@@ -16 +16 @@
-<ke_inf>&sK;</ke_inf>
+<ke_inf>&rK;</ke_inf>

進退窮まって	1641	67.0%
進退きわまって	453	18.5%
進退極まって	333	13.6%
進退谷まって	21	0.9%


進退窮まる	1305	65.3%
進退きわまる	433	21.7%
進退極まる	224	11.2%
進退谷まる	36	1.8%

no dictionary entries for 窮, and yourei and google news are exclusively 進退窮, so I'm adding 極 as [sK], even though the statistics might otherwise be high enough to display it. 極 is well-represented on twitter though, so definitely worth at least the [sK]. 

sankoku suggests that 谷 and 窮 are "technically" interchangeable, but doesn't have a dedicated entry for this expression.

@@ -10,0 +11,4 @@
+<keb>進退極まる</keb>
+<ke_inf>&sK;</ke_inf>
+</k_ele>
+<k_ele>
@@ -11,0 +16 @@
+<ke_inf>&sK;</ke_inf>

gg5, chujiten, ルミナス, wisdom

Not always figurative.

@@ -19,2 +19,10 @@
-<gloss>to be at a loss</gloss>
-<gloss>to be cornered in a situation</gloss>
+<gloss>to be driven into a corner</gloss>
+<gloss>to be left with nowhere to turn</gloss>
+<gloss>to be in a dilemma</gloss>
+</sense>
+<sense>
+<pos>&exp;</pos>
+<pos>&v5r;</pos>
+<gloss>to be unable to go forward or backward</gloss>
+<gloss>to be stranded</gloss>
+<gloss>to get stuck</gloss>

@@ -13 +13 @@
-<gloss>person of Asian descent</gloss>
+<gloss>of Asian descent</gloss>

アジア系	194392	  
アジア系の	69649	  
アジア系アメリカ	8764	  
アジア系外国	8018	  
アジア系が	6531	  
アジア系は	5569

I'd put it first, アジア系が is way down the count.

@@ -10,0 +11 @@
+<pos>&adj-no;</pos>
@@ -12 +12,0 @@
-<pos>&adj-no;</pos>

"Asian" isn't wrong per se but usually this word is things like アジア系イタリア人, e.g. an Italian person of Asian descent.
Glosses shouldn't be a mix of n and n-pref/adj. (but I wouldn't mind putting adj-no first either)

@@ -12,4 +12,2 @@
-<pos>&n-pref;</pos>
-<gloss>Asian</gloss>
-<gloss>(person) of Asian descent</gloss>
-<gloss>Asian- (e.g. Asian-American)</gloss>
+<pos>&adj-no;</pos>
+<gloss>person of Asian descent</gloss>

GG5

* Add pos [n-pref]
* …and corresponding hyphenated gloss
Used in terms like アジア系アメリカ人 (Asian-American) etc.

@@ -12,0 +12,1 @@
+<pos>&n-pref;</pos>
@@ -14,0 +15,1 @@
+<gloss>Asian- (e.g. Asian-American)</gloss>

GG5, Eijiro, ルミナス

@@ -13,2 +13,2 @@
-<xref type="see">欠くべからざる</xref>
-<xref type="see">欠くことができない</xref>
+<xref type="see" seq="2671560">欠くべからざる</xref>
+<xref type="see" seq="2671550">欠くことができない</xref>

新和英中辞典, リーダーズ+プラス, Eijiro

Useful and common expression

@@ -14,1 +14,1 @@
-<xref type="see">欠くべからざる</xref>
+<xref type="see" seq="2671560">欠くべからざる</xref>

新和英中辞典

1.4 M hits. Useful and common expression.

typo

@@ -12 +12 @@
-<pos>&adj-i;</pos>
+<pos>&adj-pn;</pos>

新和英中辞典

500k hits. Useful and common expression.