Awk print file name within for loop - for-loop

Question

I am running a for-loop over several files located in a directory. Each command within the for-loop appends the former .txt with a new column. Currently, the 3rd line in the for loop creates a column with the filepath, but I want just the filename - I don't need the file extension either. I've played around with splitting and piping back into awk, but no luck.
After adjusting the awk command to get just the filename, I want to then make a master .txt file that contains all looped values. Essentially I think I would need to append a .txt file with the output from each loop. Right now that's what I'm trying to do with the pipe in the third line of the for loop, but it just creates an empty .txt file.
for file in ~/Desktop/test/*bam
do
bedtools multicov -bams "$file" -bed bed_for_multicov.bed > "${file%%_RRemoved.bam}_counts.txt"
awk '{print $0,a}' a="$(samtools view -c "$file")" ${file%%_RRemoved.bam}_counts.txt > ${file%%_RRemoved.bam}_CPMcounts.txt
awk -v var="$file" '{print $0, var}' ${file%%_RRemoved.bam}_CPMcounts.txt > ${file%%_RRemoved.bam}_CPMcounts2.txt | >> CPMcountsMaster.txt
done
Current filename1_CPMcounts2.txt output
chr1 11088 11488 peak_1 192 4409922 path/to/filename1.bam
chr1 20674 21215 peak_2 217 4409922 path/to/filename1.bam
chr1 28550 28862 peak_3 170 4409922 path/to/filename1.bam
chr1 29582 30300 peak_4 437 4409922 path/to/filename1.bam
chr1 30635 31720 peak_5 696 4409922 path/to/filename1.bam
chr1 32373 35541 peak_6 2877 4409922 path/to/filename1.bam
Current filename2_CPMcounts2.txt output
chr1 11088 11488 peak_1 293 5888360 path/to/filename2.bam
chr1 20674 21215 peak_2 439 5888360 path/to/filename2.bam
chr1 28550 28862 peak_3 392 5888360 path/to/filename2.bam
chr1 29582 30300 peak_4 901 5888360 path/to/filename2.bam
Desired filename1_CPMCounts2.txt output
chr1 11088 11488 peak_1 192 4409922 filename1
chr1 20674 21215 peak_2 217 4409922 filename1
chr1 28550 28862 peak_3 170 4409922 filename1
chr1 29582 30300 peak_4 437 4409922 filename1
chr1 30635 31720 peak_5 696 4409922 filename1
chr1 32373 35541 peak_6 2877 4409922 filename1
Desired Final CPMcountsMaster.txt
chr1 11088 11488 peak_1 192 4409922 filename1
chr1 20674 21215 peak_2 217 4409922 filename1
chr1 28550 28862 peak_3 170 4409922 filename1
chr1 29582 30300 peak_4 437 4409922 filename1
chr1 30635 31720 peak_5 696 4409922 filename1
chr1 32373 35541 peak_6 2877 4409922 filename1
chr1 11088 11488 peak_1 293 5888360 filename2
chr1 20674 21215 peak_2 439 5888360 filename2
chr1 28550 28862 peak_3 392 5888360 filename2
chr1 29582 30300 peak_4 901 5888360 filename2

Answer 1

The following works, adapted from J Leffler's comment - thanks!
for file in ~/Desktop/test/*bam
do
bedtools multicov -bams "$file" -bed bed_for_multicov.bed > "${file%%_RRemoved.bam}_counts.txt"
awk '{print $0,a}' a="$(basename "$file" _RRemoved.bam)" ${file%%_RRemoved.bam}_CPMcounts.txt > ${file%%_RRemoved.bam}_CPMcounts2.txt
awk '{print $0,a}' a="$(basename "$file" _RRemoved.bam)" ${file%%_RRemoved.bam}_CPMcounts.txt >> CPMcountsMaster.txt
done