Index Match with multiple nested if statements

[equals]

Hi,
I have two tables, one with "source" data as follows:

A	B	C	D	E	F	G	H	I	J	K
Lookup	Helper	High	Low	Geo_Lookup	Geo_High	Geo_Low	Other	Class	Description	Important
A1	A1							11	Apples & Oranges	N
A2	#ALT							2	Apples & Pears	N
		A2						55	High Apples & Pears	Y
			A2					56	Low Apples & Pears	N
A2a	A2a							13	Oranges & Plums	Y
A2c	#ALT 2							14	Plums & Pears	N
		A2c						15	Pears & Plums High	Y
			A2c						Pears & Plums Low	Y
B1	#GEO			#GEO _ALT				1	Apples & Pears	Y
		B1							Apples & Pears High
			B1						Apples & Pears Low	Y
					B1				GEOApples & Pears High	N
						B1			GEOApples & Pears Low	Y
							B1		OTHER Apples & Pears	N
B2	B2							6	Oranges & Pears	Y
B2a								9	Kiwi & Lime	N
B3	#GEO			#GEO _ALT			#ALT	11	Lime	N
		B3							Lime High	Y
			B3						Lime Low	N
					B3				GEO Lime High	Y
						B3			Geo Lime Low	Y
...	...	...	...	...	...	...	...	...	...	...

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And a second "results" table which I wish to write some formulae for to lookup the description based upon its Geology and Height

A	B	C	D	E	F	G	H
Uid	Definition	Resolves_to	Description	Important	Geo	Height	Class
G1	A1a	A1			A	50
G2	B3	#GEO				11
G3	A2a	A2a			B	2
G4	A2	#ALT			A	200
G5	B2b	B2				5
G6	B2	B2			A	36

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The definition code is not always contained in the lookup table, but its parent code is so I am using the following formula to check if its present and remove the trailing sub category (the trailing alpha character) if it is not:
{=IFNA(VLOOKUP(B2:B13268,Source_Lookup_Table!A:M,2,FALSE),VLOOKUP(IF(ISNUMBER(-RIGHT(B2:B13268)),B2:B13268,LEFT(B2:B13268,LEN(B2:B13268)-1)),Source_Lookup_Table!A:M,2,FALSE))}

I would like to populate the "results" table columns D, E and H with the description/importance/class of the closest category.

The helper # codes need the following logic:
#ALT
Where "Source_Lookup_Table!B:B" = "#ALT " then choose between columns C (High) and D (Low) based upon Height >=50

#ALT 2
Where "Source_Lookup_Table!B:B" = "#ALT 2" then choose between columns C (High) and D (Low) based upon Height <=10

#GEO
Where "Source_Lookup_Table!B:B = "#GEO " check if "Results_Table!F:F" (Geo column) = A
If it does - Check the altitude is >=50 and lookup column F (Geo_High) or if <50 column G (Geo_Low)
If Column F (Geo) = B then check if it exists (or its non sub category) as a separate row in column H - if NA (cannot be found) then find it in Column A and then read column H which will resolve to "#ALT " and can therefore be resolved using columns C and D as above.

This is where I am at so far (although I currently have a few more columns in my sheet) - I am using index match so I can write the formulae and then just change the column number match resolves to extract the data I need:
{=IFS((M2:M13268>=50)*(G2:G13268="#ALT "),(IFNA(INDEX(Source_Lookup_Table!C:C,MATCH(E2:E13268,Source_Lookup_Table!C:C,0)),INDEX(Source_Lookup_Table!C:C,MATCH(F2:F13268,Source_Lookup_Table!C:C,0)))),(M2:M13268<50)*(G2:G13268="#ALT "),(IFNA(INDEX(Source_Lookup_Table!D:D,MATCH(E2:E13268,Source_Lookup_Table!D:D,0)),INDEX(Source_Lookup_Table!D:D,MATCH(F2:F13268,Source_Lookup_Table!D:D,0)))),(M2:M13268<=10)*(G2:G13268="#ALT 2"),IFNA(INDEX(Source_Lookup_Table!D:D,MATCH(E2:E13268,Source_Lookup_Table!D:D,0)),INDEX(Source_Lookup_Table!D:D,MATCH(F2:F13268,Source_Lookup_Table!D:D,0))),(M2:M13268>10)*(G2:G13268="#ALT 2"),IFNA(INDEX(Source_Lookup_Table!C:C,MATCH(E2:E13268,Source_Lookup_Table!C:C,0)),INDEX(Source_Lookup_Table!C:C,MATCH(F2:F13268,Source_Lookup_Table!C:C,0))),G2:G13268="#GEO ",VLOOKUP(F2:F13268,Source_Lookup_Table!A:M,5,FALSE),TRUE,G2:G13268)}

Because I have >13200 rows I am using {array formula}. but I have discovered lots of things like AND do not work so I have tried IF((A1>3)*(B1="#GEO ")) and lots of ISNUMBER statements to keep things true of false. I have managed to get somewhere with the first two bits of logic, but it has failed again when trying to implement the ""#GEO " logic.. It is also taking a very long time to calculate on my laptop, causing excel to freeze for minutes at a time so I was hoping there might be a more efficient method?

Any guidance very gratefully received.

 

[equals]

I meant to say, column E (geo_lookup) can have a value (i.e. A3b) or "#GEO_ALT" which is when I would like to check the altitude and resolve between Column F (Geo_High) and Column G (Geo_Low)