Here's the straight dope: First of all,you have a very light lathe. It looks like a HF type 7". (I'd only ever use HSS tooling in it for reasons described below.)
Second: Carbide is not the magic answer. It is never as sharp as HSS can get. It is adding to your problem,and it would be best if you use HSS boring bars on a light lathe. You are using the wrong form of boring bar anyway. Those are really for boring heads in a mill. Explanation below.
Third: Carbide does not cut as smoothly as HSS because it isn't sharp enough. There are certain inserts that are sharp,but they are for softer metals. Carbide is too brittle to keep a sharp edge in steel.
Fourth: Those cheaper carbide cutters are not really ready to use right out of the box. They need to be honed sharper. I have diamond grinders down to 3000 grit. You might get by with a CERAMIC sharpening stone. They are hard enough to hone carbide. Softer stones won't. DON't try getting by with a diamond stone. Unless it is VERY fine,it won't leave a sharp enough edge. I use Spyderco ceramic stones. I have a black one,and a finer white one. Woodcraft Supply sells a smaller size pink colored fine ceramic stone about the size of a playing card. You need to hone those carbide cutters sharp.
I seldom use carbide,unless I'm taking a cut across the face plate. Cast iron does wear HSS before I can get all the way across a 16" face plate. Most of the time,I'm using HSS. It is easy to re grind and re hone. To tell the truth,most home shop lathes are not able to push carbide to its full usefulness anyway.
Fifth: If you experiment some,you can learn how to grind a HSS lathe tool,especially a boring bar,so that it wants to suck into the cut as much as it wants to be pushed out of it. This takes experience. At least,grind a small dip on the top of your HSS boring bar so that there is a sharper cutting edge presented. The flat tops on those carbide boring bars are NOT helping you AT ALL.As seen from the top,grind the HSS tool so that the corner that cuts is the foremost edge that is presented to the work. Grind a little angle on the tool. Don't overdo it,you don't want the boring bar sucking right into the hole and breaking off,or damaging your light lathe chuck.
Sixth: Do not let any more boring bar stick out than absolutely necessary. It will then be as rigid as it can be. The style of boring bar you're using,with that tapered shank,gives you no way to adjust the amount of tool overhanging. A perfectly good HSS boring bar can be ground out from a 3/8" square lathe tool. Grind the middle area of the lathe tool thinner,so you have a teat on the cutting end,that you can sharpen into a cutter. Pros often make these small boring bars from HSS lathe tools. I use them a lot. You can also buy longer length HSS lathe tools if as regular one isn't long enough. Or,if the hole is large enough,make a boring bar as shown above by GK1918,that you can put a small 1/8" square broken off lathe tool into.
Although your lathe is small,if you have the experience,you can do good work on it.
Seventh: Tighten up the gibs on your compound,and on the cross slide while boring. This is more necessary on a light lathe more than on a larger one. The little lathe is only so rigid to begin with. DO TIGHTEN the gibs. Make them snug enough that you can turn the handles,but with a little resistance. You can and should loosen them back to normal when you are done boring. The gibs being too loose can also make trouble with cutting off. When I had an Atlas 12" lathe,cutting off was not my favorite job. And,the Atlas was a much heavier one than yours.
