Hi Desco, The white foam is from condensation. I've seen this several times on good working motors. The condensation is normal.
If you road bike several miles & got it hot the white would disappear. Always important to change primary oil as it really collects condensation.
Good you have a filter. What filter are you using.
Regarding the crank seal, since oil pressure is good, it's very unlikely it's split or turned out. Same with oil pump.
Since motor sump has normal amount of oil in it the return pump is working. I knew that or you'd have filled motor with oil & frame would be low by that amount.
The spurts are caused by pump sucking dry, then oil fill enough in motor sump to suck oil & send it back quickly.
On my bike it spurts at idle, but once you get to 1500rpm & higher it is almost a steady stream. At 4000 it looks like a strong squirt with no visible gaps in oil. A slight pulsation in stream is all you see.
You can test return pump using a vacuum gauge. Shop manual
covers this. I've done the test a few times. I warm motor, pull sump drain/screen & attach rubber hose to steel pipe. Adapt that hose to any vacuum gauge. Start motor. The vacuum almost instantly goes to 22-24". Turning off motor it takes a long time to drop. Mine didn't just drop off. Of course oil streams out of sump with engine running so put a catch pan under it.
I don't know why your oil would get dirty so fast. After bike has been ran the oil will aeriate very quickly. That is normal also.
Now are we getting back to my curiosity of the differential between the return orifice & the rocker feed orifice?
Is the rockers getting too much oil & oil is recirculating from top end, yet the return pump can send enough to tank to not fill motor?? It seems like it could be happening??
This is where exact knowledge of the return system may help you. I obviously don't have exact knowledge. That's why I'm so curious about how factory determined this.