I am having some trouble understanding my samtools tview output.

press 'H' to get help. '.' is match on forward strand ',' is match on negative strand.

'R' to show the bases.

R/M/S mean in the second line

consensus with degenerate nucleotide alphabet https://en.wikipedia.org/wiki/Nucleic_acid_notation

R/M/S are standard IUPAC ambiguity codes that are shown if you have mismatches/variants at a site. Note that *** indicates an insertion. Underlined reads are either secondary alignments or orphans (hit ? and look at the bottom). If the reads are colored, then that indicates their MAPQ.

I have absolutely no idea what you want to achieve by removing indels or SNPs. Regarding errors, I suppose any difference that isn't called a variant could in theory be called an error and changed in the BAM file, but as a general rule that's a really bad idea. It's best to explain what your actual goal is.