Slow Performance and ODBC errors Access with SQL 2000 backend

Access experts -

I have just started @ a company with a homegrown(written 3 years ago) Access 2000 .mdb frontend and ODBC linked SQL 2000 tables in backend (with DTS ) appl. Initially it work well & fast with approx. 60 users split in 2 locations with majority of remote users using a Terminal server.
The data trans. service agents run overnite & a few during the day.
Performance has gone down & besides slowness ( up to 20 minutes back east ) there are ODBC timeouts , the SQL server seems not to be blocking ( only once in a while ) or deadlocking - what has change ?
1. Actually management says - there are FEWER users now then before about 50 now.
2.They have moved the SQL server to an upgraded server box  with 3GB memory , faster CPU,  larger drive RAID 5 config & network people indicate the server is not being overworked (less than 50% capacity) through the server logs.

3. Problem appears the database which is 34GB in size now has many more records - there is 1 history(Hist) table over 1,200,000 records and 145 column fields & some others about 400,000 and then others in the 50,000 range (Curr) current  along with some 60 other less used tables.

4.The Access program calls a SQL (FIND_ID)store procedure to do record_ID lookup & status check in  Hist table  &  Curr table- this is on every Access form (over 250) - open form or recordsource event, report event etc - this routine is peppered throughout .

5. In the program as well there are ALSO many query calls from Acess to create open record sets , fill in parameters & build reports etc. from Hist & Curr. databases and other linked tables .

The program has ODBC linked SQL tables & after log in has a "transfer Database ac_link" routine.
 
I see a querydef as shown below--   GetID ( ) gets the prime record reference ID from the current form & the I_StatusCk --stored prc..
checks existing primeID record in Hist or Curr tables then builds out record with parameter data
Find_ID is used on every form , report etc.. Below - I had to type it might be some typos - but the code does work -- the prblem is Slowness


Public Function Find_ID( )
Dim FIDB as Database, FIQdf as Querydef, FIRst as RecordSet, FISQL as String

FISQL ="EXECUTE I_StatusCk @GetPrime =" & GetID( ) & " , @UserID = '"& GetCurrUser & '"

Set FIDB = CurrentDB
SET FIQdf=FIDB.CreateQueryDef("")
FIQdf.ODBCTimeOut = 300                        '>>>>>>>   Here I can change this to help ODBC timeout - but slowness will continue....

With FIQdf
.Connect=ConSource
'.Prepare=dbQUnprepare
.SQL=FISQL
.ReturnRecords=False
.Execute dbSQLPassThrough
FISQL="SELECT RepStatus.Status FROM RepStatus WHERE"
FISQL=FISQL & "((RepStatus.R_ID)=" & GetID( ) &");"

set FIRst=FIDB.OpenRecordSet(FISQL,dbOpenSnapshot)
FIRst.MoveLast
ARAFind=FIRst![Status]
FIRst.Close
FIQdf.Close
End With
Set FIDB=Nothing

END Function

I have to fix this by next month with out any major coding changes per IT manager (premise is that it WORKED before and to minimize risk to production). I have proposed to archived off half of Hist table but I do not think this will be much help.
Other option would be moving mdb app to ADP but with over 250 forms, reports , extensive code with modules etc.. Is there an automated transfer or conversion process ?? Would this help this ???
Please help - I am going to post this SQL side as well but the bottle neck again seems to be with the fat Access current configuration...