........... anyway ...Does or did the oil level look low on the dipstick ?? , if not , then it should not have been a factor , most all of us run 1 full quart in the transmission side , but the engine we use the recommended amount , and I don't know of any failures related to running the correct amount of oil , so I would say , No , the foaming issue would not be a factor in this case , I run 10-40 in both my bikes , I have used Shell Rotella full synthetic , and Maxima full synthetic , and Amsoil , I currently have Maxima in my 450X and Amsoil Dirt in my 450R (appropriately named) and have never had any kind of failure in 12 years of doing so , let alone any oil related failure , it is possible that the rocker just went on its own as Ray mentioned , but generally there is a underlying factor that led up to it failing
Personally , my "next step" would be to go thru the top end , obviously replacing the head with what you can afford , and maybe splitting the cases , to make sure all debris is removed , then replace the Timing Chain (a regular maintenance item anyway and inexpensive) , check the piston for skirt wear , if its under 100 hours , it should look relatively free from skirt damage with maybe some normal wear marks which would look like you took steel wool to it , nothing more than that , if it looks good re-assemble , or if you can swing it , put a new piston in (I would personally recommend a JE 12.5 or 13.0-1 at around $150) , and i would manually test the oil pump by removing it and sticking the pickup in a tub of oil and spinning the gear , it should pick up the oil and have resistance on it and pump out the oil relatively quickly
You could actually get away with finding just a used tower which would include the cam and rocker , and you need to replace that regardless , then do what is within you budget with the rest for now , then later on maybe save up for a new piston , etc , but i would at the very least , replace the head , even with a complete used one for now , then plan on valves during winter maintenance downtime , and then do the chain , piston , etc , and look over the clutch plates and look at the clutch basket for grooving , and you will be ready to go in spring and have a bike that should last several seasons before needing anything other than oil/filter changes and a clean air filter every ride.....
Or go the economy route:
My main concern is if the oil pump is fine along with the filter , then at the very least , use a magnet to feel around for any look particles , then clean up the areas where you found debris , then flush the engine out with some cheap oil from the head down (pour it right in the top of the head , use a quart or 2) , tipping it from side to side once the oil drains to the bottom ,then leaving it leaning on the kickstand for draining (with the ignition cover on to fill with a few bottom bolts snugged down , then removed the cover to drain the oil so you get full flow of any debris into the pan) , if you do not find any more debris in the pan , then replace that tower as i mentioned and install the new/used tower reinstall the ignition cover , and with the tank removed and the valve cover just snugged down with 2 bolts , fire it up , then shut it off if all sounds good after 30-40 seconds of running , and remove the valve cover to verify the oil is at the top end , if its good , then tighten everything down , and go ride
) However, after draining the oil and opening the left side crankcase, I saw way less than .7L. This started to make me wonder (along with past experience) that I may have too little of oil in the system (as I did not check the oil enough).
, unless of course your only riding it a few times every few months , you CAN go extended periods using synthetic , I do this myself in my X , but , generally I change at least 2 times a season , when i ride maybe 10 rides on the oil (as I usually ride my 450R every weekend , so the X sits a lot lately) , for example , i have only rode it 1 time this year , otherwise i am on my R , as i was today at the track , then again tomorrow and Sunday most likely , so my R gets a workout , the X lately not so much , my R with Amsoil gets about 6 rides per filter and oil change before I feel uncomfortable , my X i dont abuse as much as my R so its less frequent but still just a few rides more than my R , these engines will "use" some oil , basically when i see the level drop in the window on my R , or the Dipstick on the X , then that means its past due to be changed , which equates to about 6 hard rides on the R and about 10 or so on the X 
